* app/plug-in/plug-in-rc.c: implement a new pluginrc flag,
 	"has-init", so that only plug-ins with init functions are
 	initialized.

	* app/plug-in/plug-in.ch
 	* libgimp/gimp.c
 	* libgimpbase/gimpprotocol.ch: send a new gimpwire message,
 	GP_HAS_INIT during the query stage if the plug-in needs to be
 	initialized.  Only invoke the plug-in in init mode if the plug-in
 	has an init function.