fix format string warning

git-svn-id: svn://anonsvn.kde.org/home/kde/trunk/KDE/kdenetwork/krfb/libvncserver@647260 283d02a7-25f6-0310-bc7c-ecb5cbfe19da

main.c

@@ -74,7 +74,7 @@ rfbLog(const char *format, ...)
 
     time(&log_clock);
     strftime(buf, 255, "%d/%m/%Y %T ", localtime(&log_clock));
-    fprintf(stderr,buf);
+    fprintf(stderr,"%s", buf);
 
     vfprintf(stderr, format, args);
     fflush(stderr);