libprelude: fixed to install perl modules into vendor directory (see note!)

Note:

According to:

http://search.cpan.org/dist/perl/INSTALL#Installation_Directories

this is the right place for distributions which build binary packages of
perl add-on modules.

security/libprelude/libprelude.conf

@@ -17,3 +17,7 @@ if [ $prefix_auto = 1 ] ; then
         set_confopt
 fi
 
+if pkginstalled perl; then
+	# install perl modules into vendor
+	var_append extraconfopt ' ' "--with-perl-installdirs=vendor"
+fi