rrdtool: fixed to install perl modules into 'vendor_perl' directory

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.

database/rrdtool/rrdtool.conf

@@ -2,7 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../rrdtool/rrdtool.conf
-# Copyright (C) 2006 - 2009 The OpenSDE Project
+# Copyright (C) 2006 - 2011 The OpenSDE Project
 # Copyright (C) 2004 - 2006 The T2 SDE Project
 # Copyright (C) 1998 - 2003 Clifford Wolf
 #
@@ -24,7 +24,8 @@ pkginstalled python || var_append extraconfopt ' ' "--disable-python"
 
 # perl support
 if pkginstalled perl ; then
-	var_append confopt ' ' "--enable-perl-site-install"
+	# install perl modules into 'vendor_perl' directory
+	var_append extraconfopt ' ' "--with-perl-options='INSTALLDIRS=vendor'"
 else
 	var_append extraconfopt ' ' "--disable-perl"
 fi