hgcommand.vim: refer Vim7 users to vcscommand plugin

contrib/vim/hgcommand.vim

@@ -10,6 +10,12 b''
 "                Bob Hiestand <[e-mail]> for the fabulous
 "                cvscommand.vim from which this script was directly created by
 "                means of sed commands and minor tweaks.
+" Note:          
+"                For Vim7 the use of Bob Hiestand's vcscommand.vim
+"                <http://www.vim.org/scripts/script.php?script_id=90>
+"                in conjunction with Vladmir Marek's Hg backend
+"                <http://www.vim.org/scripts/script.php?script_id=1898>
+"                is recommended.
 
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 "