Windows: Always set the system timer resolution to 1ms by default.

An existing hint lets apps that don't need the timer resolution changed avoid
this, to save battery, etc, but this fixes several problems in timing, audio
callbacks not firing fast enough, etc.

Fixes Bugzilla #2944.

test/relative_mode.markdown

@@ -0,0 +1,58 @@
+Relative mode testing
+=====================
+
+See test program at the bottom of this file.
+
+Initial tests:
+
+ - When in relative mode, the mouse shouldn't be moveable outside of the window.
+ - When the cursor is outside the window when relative mode is enabled, mouse
+   clicks should not go to whatever app was under the cursor previously.
+ - When alt/cmd-tabbing between a relative mode app and another app, clicks when
+   in the relative mode app should also not go to whatever app was under the
+   cursor previously.
+
+
+Code
+====
+
+    #include <SDL.h>
+
+    int PollEvents()
+    {
+        SDL_Event event;
+        while (SDL_PollEvent(&event))
+        {
+            switch (event.type)
+            {
+                case SDL_QUIT:
+                    return 1;
+                default:
+                    break;
+            }
+        }
+
+        return 0;
+    }
+
+    int main(int argc, char *argv[])
+    {
+        SDL_Window *win;
+
+        SDL_Init(SDL_INIT_VIDEO);
+
+        win = SDL_CreateWindow("Test", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, 0);
+        SDL_SetRelativeMouseMode(SDL_TRUE);
+
+        while (1)
+        {
+            if (PollEvents())
+                break;
+        }
+
+        SDL_DestroyWindow(win);
+
+        SDL_Quit();
+
+        return 0;
+    }