better fix for missing __FUNCTION__

git-svn-id: http://svn.openzap.org/svn/openzap/trunk@489 a93c3328-9c30-0410-af19-c9cd2b2d52af

libs/openzap/src/include/zap_types.h

@@ -437,7 +437,7 @@ typedef zap_status_t (*zio_write_t) ZIO_WRITE_ARGS ;
 #define ZIO_WRITE_FUNCTION(name) zap_status_t name ZIO_WRITE_ARGS
 
 #ifndef __FUNCTION__
-#define __FUNCTION__ ""
+#define __FUNCTION__ (const char *)__func__
 #endif
 
 #define ZAP_PRE __FILE__, __FUNCTION__, __LINE__