Updated library name in header file.

include/SDL_thread.h

@@ -74,15 +74,15 @@ typedef int (SDLCALL * SDL_ThreadFunction) (void *data);
  *
  *  We compile SDL into a DLL. This means, that it's the DLL which
  *  creates a new thread for the calling process with the SDL_CreateThread()
- *  API. There is a problem with this, that only the RTL of the SDL.DLL will
+ *  API. There is a problem with this, that only the RTL of the SDL2.DLL will
  *  be initialized for those threads, and not the RTL of the calling
  *  application!
  *
  *  To solve this, we make a little hack here.
  *
  *  We'll always use the caller's _beginthread() and _endthread() APIs to
- *  start a new thread. This way, if it's the SDL.DLL which uses this API,
- *  then the RTL of SDL.DLL will be used to create the new thread, and if it's
+ *  start a new thread. This way, if it's the SDL2.DLL which uses this API,
+ *  then the RTL of SDL2.DLL will be used to create the new thread, and if it's
  *  the application, then the RTL of the application will be used.
  *
  *  So, in short: