Valgrind 3.4.0 is pretty new, and even if --track-origins is a nice
feature, it is not the end of the world if that is not available.  So
play nice and use that option only when only an older version of
valgrind is available.

In the same spirit, refrain from the use of '...' in suppression
files, which is also a feature only valgrind 3.4 and newer understand.
Signed-off-by: NJohannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>