Fix failing to set high priority for threads on Linux desktop.

Debugging inside rtkit showed we were failing the RLIMIT_RTTIME check, now that we're asking for realtime and not just high-priority due to a change in SDL.

Between that and the DBus code in SDL being wrong in previous changelist I'm not sure how this could have ever worked.

src/core/linux/SDL_threadprio.c

@@ -106,7 +106,8 @@ rtkit_initialize_thread()
         return SDL_FALSE;
     }
 
-    rlimit.rlim_cur = rlimit.rlim_max;
+    // Current rtkit allows a max of 200ms right now
+    rlimit.rlim_cur = rlimit.rlim_max = 100000;
     err = setrlimit(nLimit, &rlimit);
     if (err)
     {