Added a note to direct people to README-migration.md

WhatsNew.txt

@@ -11,7 +11,7 @@ General:
 * SDL_GetWindowWMInfo() returns a standard int result code instead of SDL_bool, and takes SDL_SYSWM_CURRENT_VERSION as a new third parameter
 * The preprocessor symbol __MACOSX__ has been renamed __MACOS__
 * The preprocessor symbol __IPHONEOS__ has been renamed __IOS__
-* Removed the following functions from the API:
+* Removed the following functions from the API, see docs/README-migration.md for details:
 	* SDL_CalculateGammaRamp()
 	* SDL_GetRevisionNumber()
 	* SDL_GetWindowBrightness()
@@ -19,7 +19,7 @@ General:
 	* SDL_RWFromFP()
 	* SDL_SetWindowBrightness()
 	* SDL_SetWindowGammaRamp()
-* Removed the following hints from the API:
+* Removed the following hints from the API, see docs/README-migration.md for details:
 	* SDL_HINT_IDLE_TIMER_DISABLED
 	* SDL_HINT_VIDEO_X11_FORCE_EGL
 	* SDL_HINT_VIDEO_X11_XINERAMA