Cleaned up and rearranged WinRT project file structure.

All WinRT projects have been merged into a single directory, "VisualC-WinRT",
with platform-specific variants in subdirectories off of it.  This structure
has been applied to a few major SDL satellite libraries as well (SDL_image,
SDL_mixer, and SDL_ttf).

Currently, only Windows 8.0/RT and Windows Phone 8.0 targets are supported.
Windows 8.1/RT/Phone targets are planned.

Projects that use SDL_image/WinRT, and link to it via Visual Studio's
project-to-project reference system, will need to be updated, to reflect the
changes in the project structure.  This can be done by:
1. removing the MSVC project(s) for SDL/WinRT
2. re-added the MSVC project(s) for SDL/WinRT
3. right-clicking on the app, or projects that use those libraries, choosing
References, removing the references to any of these projects (they'll likely
be highlighted with an exclamation mark), then re-adding them

To note, the satellite libraries that reference SDL/WinRT have been updated
already.  The changes for those libraries will be pushed to hg.libsdl.org
shortly.

TODO:
- add support for Windows 8.1 and Windows Phone 8.1 targets, using
Microsoft's new "Universal" app support, if possible.  These will be added to
a new subdirectory, or subdirectories (if more than one sets of projects are
needed, hopefully not), of "VisualC-WinRT".
- investigate NuGet support, which could allow Visual C++ to download
new copies of SDL/WinRT, its satellite libraries, and their dependencies,
from remote servers.

VisualC-WinRT/WinPhone80_VS2012/SDL-WinPhone80.vcxproj

@@ -23,7 +23,7 @@
     <RootNamespace>SDL</RootNamespace>
     <DefaultLanguage>en-US</DefaultLanguage>
     <MinimumVisualStudioVersion>11.0</MinimumVisualStudioVersion>
-    <ProjectName>SDL2-WinPhone</ProjectName>
+    <ProjectName>SDL2-WinPhone80</ProjectName>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
@@ -62,15 +62,19 @@
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|ARM'">
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|ARM'">
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>

VisualC-WinRT/WinRT80_VS2012/SDL-WinRT80.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 2012
-Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "SDL-WinRT", "SDL\SDL-WinRT_VS2012.vcxproj", "{AEAEA3A2-D4E6-45B1-8EC6-53D84287FC14}"
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "SDL-WinRT", "SDL-WinRT80.vcxproj", "{AEAEA3A2-D4E6-45B1-8EC6-53D84287FC14}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

VisualC-WinRT/WinRT80_VS2012/SDL-WinRT80.vcxproj

@@ -347,7 +347,7 @@
   <PropertyGroup Label="Globals">
     <ProjectGuid>{aeaea3a2-d4e6-45b1-8ec6-53d84287fc14}</ProjectGuid>
     <Keyword>Win32Proj</Keyword>
-    <ProjectName>SDL2-WinRT</ProjectName>
+    <ProjectName>SDL2-WinRT80</ProjectName>
     <RootNamespace>SDL_VS2012_WinRT</RootNamespace>
     <DefaultLanguage>en-US</DefaultLanguage>
     <MinimumVisualStudioVersion>11.0</MinimumVisualStudioVersion>
@@ -412,31 +412,37 @@
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|ARM'">
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|ARM'">
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
     <GenerateManifest>false</GenerateManifest>
     <IgnoreImportLibrary>false</IgnoreImportLibrary>
     <TargetName>SDL2</TargetName>
+    <IntDir>Objs\$(Platform)\$(Configuration)\$(MSBuildProjectName)\</IntDir>
   </PropertyGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
     <ClCompile>

VisualC-WinRT/tests/loopwave/loopwave_VS2012.vcxproj

@@ -160,7 +160,7 @@
     <Media Include="..\..\..\test\sample.wav" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\SDL\SDL-WinRT_VS2012.vcxproj">
+    <ProjectReference Include="..\..\WinRT80_VS2012\SDL-WinRT80.vcxproj">
       <Project>{aeaea3a2-d4e6-45b1-8ec6-53d84287fc14}</Project>
     </ProjectReference>
   </ItemGroup>

VisualC-WinRT/tests/testthread/testthread_VS2012.vcxproj

@@ -150,7 +150,7 @@
     <ClCompile Include="..\..\..\test\testthread.c" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\SDL\SDL-WinRT_VS2012.vcxproj">
+    <ProjectReference Include="..\..\WinRT80_VS2012\SDL-WinRT80.vcxproj">
       <Project>{aeaea3a2-d4e6-45b1-8ec6-53d84287fc14}</Project>
     </ProjectReference>
   </ItemGroup>