collectd: 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.

monitor/collectd/collectd.conf

@@ -19,6 +19,12 @@ fi
 
 var_append GCC_WRAPPER_REMOVE ' ' '-Werror'
 
+# perl bindings
+if pkginstalled perl; then
+	# options passed to "perl Makefile.PL"
+	var_append extraconfopt ' ' "--with-perl-bindings='INSTALLDIRS=vendor'"
+fi
+
 # apache plugin
 pkginstalled apache || var_append confopt ' ' "--disable-apache"