t/README: Add a note about running commands under valgrind
t/README: Add a note about running commands under valgrind

The test suite runs valgrind with certain options activated. Add a
note saying how to run commands under the same conditions as the test
suite does.

Signed-off-by: Carlos Martín Nieto <eecb638c0e60875b4a70118790d5be43bb59c2d6@elego.de>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git