Rearrange documentation

1) Moves all READMEs to docs/
2) Renames them to *.md, adds some Markdown with the idea to add a lot more
3) Moves the doxyfile config to doc/ and makes it parse the headers at ../include as well as the md files in docs.
4) Skips SDL_opengl*.h headers from the docs
5) Minor fixes to doxyfile

include/SDL.h

@@ -25,41 +25,6 @@
  *  Main include header for the SDL library
  */
 
-/**
- *  \mainpage Simple DirectMedia Layer (SDL)
- *
- *  http://www.libsdl.org/
- *
- *  \section intro_sec Introduction
- *
- *  Simple DirectMedia Layer is a cross-platform development library designed
- *  to provide low level access to audio, keyboard, mouse, joystick, and
- *  graphics hardware via OpenGL and Direct3D. It is used by video playback
- *  software, emulators, and popular games including Valve's award winning
- *  catalog and many Humble Bundle games.
- *
- *  SDL officially supports Windows, Mac OS X, Linux, iOS, and Android.
- *  Support for other platforms may be found in the source code.
- *
- *  SDL is written in C, works natively with C++, and there are bindings 
- *  available for several other languages, including C# and Python.
- *
- *  This library is distributed under the zlib license, which can be found
- *  in the file "COPYING.txt".
- *
- *  The best way to learn how to use SDL is to check out the header files in
- *  the "include" subdirectory and the programs in the "test" subdirectory.
- *  The header files and test programs are well commented and always up to date.
- *  More documentation and FAQs are available online at:
- *      http://wiki.libsdl.org/
- *
- *  If you need help with the library, or just want to discuss SDL related
- *  issues, you can join the developers mailing list:
- *      http://www.libsdl.org/mailing-list.php
- *
- *  Enjoy!
- *      Sam Lantinga                (slouken@libsdl.org)
- */
 
 #ifndef _SDL_H
 #define _SDL_H