Per http://cygwin.com/ml/cygwin/2012-07/msg00331.html , cygwin 1.7
was modified to explicitly support git's use of pread, so make this
the default. Do not affect earlier cygwin versions.
Signed-off-by: Mark Levedahl <mlevedahl@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>