Building the plugin on a platform like Fedora Rawhide (and probably Debian or Mandriva) fails due to an underlinking issue; panel-plugin does not explicitly link against (or pull CFLAGS from) xfcegui. Patch attached. (Also had to add a check for xfcegui to configure.ac to get the libs and cflags).
Created attachment 3352 fixes underlink issues
*** This bug has been marked as a duplicate of bug 6620 ***