Set SDL2 app name hint

From SDL2 source

/**
 *  \brief Specify an application name.
 * 
 * This hint lets you specify the application name sent to the OS when
 * required. For example, this will often appear in volume control applets for
 * audio streams, and in lists of applications which are inhibiting the
 * screensaver.  You should use a string that describes your program ("My Game
 * 2: The Revenge")
 *
 * Setting this to "" or leaving it unset will have SDL use a reasonable
 * default: probably the application's name or "SDL Application" if SDL
 * doesn't have any better information.
 *
 * Note that, for audio streams, this can be overridden with
 * SDL_HINT_AUDIO_DEVICE_APP_NAME.
 *
 * On targets where this is not supported, this hint does nothing.
 */
#define SDL_HINT_APP_NAME "SDL_APP_NAME"

Sometimes on apps like PulseAudio Volume Control the app name was not showing up properly

But adding this fixed it

Taken from https://github.com/P-AS/srb2-legacy/commit/49c266fec599bd699373b25ec7a25553bf850339