Some platforms ship Perl modules used by git scripts outside the
default perl path (e.g., on Mac OS X, Subversion's perl bindings live
in a separate xcode perl path). Add an PERLLIB_EXTRA variable to hold
a colon-separated list of extra directories to add to the perl path in
git's scripts, as a convenience for packagers.
Requested-by: Dave Borowitz <dborowitz@google.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>