repoman: unroll escaped lines so we can check the entirety of it

repoman: unroll escaped lines so we can check the entirety of it

Sometimes people wrap long lines in their ebuilds to make it easier to
read, but this causes us issues when doing line-by-line checking.  So
automatically unroll those lines before passing the full content down
to our checkers.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>