UNINST changet to 0. Uninstalling on system with installed already gimp

* UNINST changet to 0. Uninstalling on system with installed already gimp
perl modules during installing gimp builded from non-root account cause
failing installing procedure (patch by Piotr Czerwiski <pius@pld.org.pl>).
For uninstalling we have separated target (uninstall) and install must _only_
.. install.

plug-ins/perl/Makefile.PL

@@ -139,7 +139,7 @@ install ::
 	      exit ; \
 	   fi \
 	done ; \
-	$(MAKE) UNINST=1 really-install install-plugins'."
+	$(MAKE) UNINST=0 really-install install-plugins'."
 	$main::dont_embed || (cd embed && \$(MAKE) install)
 
 ".$install;