Added basic Gentoo metadata.xml checker.

syntax_checkers/gentoo_metadata.vim

@@ -0,0 +1,37 @@
+"============================================================================
+"File:        gentoo-metadata.vim
+"Description: Syntax checking plugin for Gentoo's metadata.xml files
+"Maintainer:  James Rowe <jnrowe at gmail dot com>
+"License:     This program is free software. It comes without any warranty,
+"             to the extent permitted by applicable law. You can redistribute
+"             it and/or modify it under the terms of the Do What The Fuck You
+"             Want To Public License, Version 2, as published by Sam Hocevar.
+"             See http://sam.zoy.org/wtfpl/COPYING for more details.
+"
+"============================================================================
+
+" The DTDs required to validate metadata.xml files are available in
+" $PORTDIR/metadata/dtd, and these local files can be used to significantly
+" speed up validation.  You can create a catalog file with:
+"
+"   xmlcatalog --create --add rewriteURI http://www.gentoo.org/dtd/ \
+"       ${PORTDIR:-/usr/portage}/metadata/dtd/ /etc/xml/gentoo
+"
+" See xmlcatalog(1) and http://www.xmlsoft.org/catalog.html for more
+" information.
+
+if exists("loaded_gentoo_metadata_syntax_checker")
+    finish
+endif
+let loaded_gentoo_metadata_syntax_checker = 1
+
+"bail if the user doesn't have xmllint installed
+if !executable("xmllint")
+    finish
+endif
+
+runtime syntax_checkers/xml.vim
+
+function! SyntaxCheckers_gentoo_metadata_GetLocList()
+    return SyntaxCheckers_xml_GetLocList()
+endfunction