Fix crash with @security (bug 488820)
EbuildBuild: handle empty PORTAGE_BINPKG_FORMAT

Also, make TaskSequence._start_next_task() call exit hooks if the
queue happens to be empty.

X-Gentoo-Bug: 506186
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=506186
make.conf.5: Fix order of some paragraphs.
Update RELEASE-NOTES
repoman: Add DESCRIPTION.puntuation check (bug #438976)

Basic patch supplied by Michael Orlitzky.
Modified to be easier to add/remove puntuation to the check.
repoman: Add ruby18 warning for deprecated ruby target