Patched to compile on Linux with threads enabled. (whoops!)
diff --git a/src/core/linux/SDL_dbus.c b/src/core/linux/SDL_dbus.c
index c227419..072767f 100644
--- a/src/core/linux/SDL_dbus.c
+++ b/src/core/linux/SDL_dbus.c
@@ -24,6 +24,8 @@
#if !SDL_THREADS_DISABLED
#include <sys/time.h>
#include <sys/resource.h>
+#include <pthread.h>
+#include "SDL_system.h"
#endif
#if SDL_USE_LIBDBUS