style: Change maximum line length to 79 characters

style: Change maximum line length to 79 characters

The old style guide used to mandate 78 characters as the maximum line
length to accommodate traditional diffs on 80-column terminals. This
is an uncommon use case and it has therefore been decided (see email
thread on gem5-dev [1]) that a maximum length of 79-characters makes
more sense.

[1] http://comments.gmane.org/gmane.comp.emulators.m5.devel/29789

Signed-off-by: Andreas Sandberg <aandreas.sandberg@arm.com>
Reviewed-by: Brandon Potter <brandon.potter@amd.com>
--HG--
rename : util/style.py => util/hgstyle.py
extra : rebase_source : 63efcc4da2585ef8c323d6f322736f64d71742f8