Add a test program of sorts, for XBEGIN and XTEST.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13579 a5019735-40e9-0310-863c-91ae7b9d1cf9
ensure nightly regression tests can (optionally) run perf tests


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13580 a5019735-40e9-0310-863c-91ae7b9d1cf9