WinRT: more renaming of "windowsrt" to "winrt"

include/SDL_main.h

@@ -44,7 +44,7 @@
    creating an instance of IFrameworkView in the process.
 
    Please note that #include'ing SDL_main.h is not enough to get a main()
-   function working.  The file, src/main/windowsrt/SDL_WinRT_main.cpp, or a copy
+   function working.  The file, src/main/winrt/SDL_WinRT_main.cpp, or a copy
    of it, must be compiled into the app itself.
 */
 #define SDL_MAIN_NEEDED