RISCOS: attempt to fix compilation ERANGE
diff --git a/src/thread/pthread/SDL_systhread.c b/src/thread/pthread/SDL_systhread.c
index 473c710..75a03ab 100644
--- a/src/thread/pthread/SDL_systhread.c
+++ b/src/thread/pthread/SDL_systhread.c
@@ -41,6 +41,10 @@
#include "../../core/linux/SDL_dbus.h"
#endif /* __LINUX__ */
+#if __RISCOS__
+# include <errno.h>
+#endif
+
#if (defined(__LINUX__) || defined(__MACOSX__) || defined(__IPHONEOS__)) && defined(HAVE_DLOPEN)
#include <dlfcn.h>
#ifndef RTLD_DEFAULT