Expose the keymap separately from the event keycode

This adds functions to query the keymap:
* SDL_GetCurrentKeymap()
* SDL_GetKeymapKeycode()
* SDL_GetKeymapScancode()
* SDL_ReleaseKeymap()

and these are distinct from the function to query the event keycode associated with a scancode, which might be affected by SDL_HINT_KEYCODE_OPTIONS.

Also added an SDL_bool parameter to SDL_GetKeyName() and SDL_GetKeyFromName() to enable upper case handling of the name.

src/test/SDL_test_common.c

@@ -1717,7 +1717,7 @@ void SDLTest_PrintEvent(const SDL_Event *event)
                 event->key.windowID,
                 event->key.scancode,
                 SDL_GetScancodeName(event->key.scancode),
-                event->key.key, SDL_GetKeyName(event->key.key),
+                event->key.key, SDL_GetKeyName(event->key.key, SDL_TRUE),
                 modstr);
         break;
     }