Add MYMETA.yml to perl/.gitignore

This file is auto-generated by newer versions of ExtUtils::MakeMaker
(presumably starting with the version shipping with Perl 5.14). It just
contains extra information about the environment and arguments to the
Makefile-building process, and should be ignored.
Signed-off-by: NSebastian Morr <sebastian@morr.cc>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

perl/.gitignore

 perl.mak
 perl.mak.old
+MYMETA.yml
 blib
 blibdirs
 pm_to_blib