strchr.vgtest mc_replace_strmem.c [r]index and [__GI_]str[r]chr are the same.

Add memcheck/tests/filter_strchr to make it so for the testcase.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13370 a5019735-40e9-0310-863c-91ae7b9d1cf9