Add unit tests for utility.c

Also fixes returned value from Memset().  And SafeMemcmp() should
return 0 (equal) if comparing 0 bytes, to match the behavior of memcmp().

BUG=chromium-os:17564
TEST=make && make runtests

Change-Id: Id43e70eecf04815216e1fd952271af35e0a66396
Reviewed-on: http://gerrit.chromium.org/gerrit/6539
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Tested-by: Randall Spangler <rspangler@chromium.org>
4 files changed