st/egl: Add extern "C" wrapper to native.h.

This allows a backend to be written in C++.

src/gallium/state_trackers/egl/common/native.h

@@ -34,6 +34,10 @@
 #include "pipe/p_state.h"
 #include "state_tracker/sw_winsys.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include "native_modeset.h"
 
 /**
@@ -237,4 +241,8 @@ native_get_drm_platform(void);
 const struct native_platform *
 native_get_fbdev_platform(void);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _NATIVE_H_ */