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.

test/testime.c

@@ -1209,7 +1209,7 @@ int main(int argc, char *argv[])
                         event.key.scancode,
                         SDL_GetScancodeName(event.key.scancode),
                         SDL_static_cast(Uint32, event.key.key),
-                        SDL_GetKeyName(event.key.key));
+                        SDL_GetKeyName(event.key.key, SDL_TRUE));
                 break;
             }
             case SDL_EVENT_TEXT_INPUT: {