vdpau: do not export _vdp_DRI2* functions

Neither one is part of the public API, thus should never be used outside
of the library itself.

Add macro PRIVATE, that is used to annotate the function visibility by
setting __attribute__((visibility("hidden"))).

v2: Provide only PRIVATE macro. Requested by Aaron.
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Aaron Plattner <aplattner@nvidia.com>
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>

src/mesa_dri2.h

@@ -37,17 +37,24 @@
 
 #include <X11/extensions/dri2tokens.h>
 
-extern Bool
+#if (defined(__GNUC__) && __GNUC__ >= 4)
+  #define PRIVATE __attribute__ ((visibility("hidden")))
+#else
+  #define PRIVATE
+#endif
+
+
+PRIVATE extern Bool
 _vdp_DRI2QueryExtension(Display * display, int *eventBase, int *errorBase);
 
-extern Bool
+PRIVATE extern Bool
 _vdp_DRI2QueryVersion(Display * display, int *major, int *minor);
 
-extern Bool
+PRIVATE extern Bool
 _vdp_DRI2Connect(Display * display, XID window, char **driverName,
                  char **deviceName);
 
-extern void
+PRIVATE extern void
 _vdp_DRI2RemoveExtension(Display * display);
 
 #endif