drd: Add strrchr(), memchr(), memrchr() and memcmp() intercepts (#326623)


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13696 a5019735-40e9-0310-863c-91ae7b9d1cf9
drd: Add a test for the strmem intercepts

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13697 a5019735-40e9-0310-863c-91ae7b9d1cf9