Bug 321730 Add cg_merge and cg_diff man pages.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13442 a5019735-40e9-0310-863c-91ae7b9d1cf9
Bug 321738 Add manpages for vgdb and valgrind-listener.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13443 a5019735-40e9-0310-863c-91ae7b9d1cf9