fcaps.eclass: Remove sys-libs/libcap-ng support
libcap-ng-0.7.10 changed the output format slightly (in upstream commit
bc1a9c07ebf5 "- Add capng_have_permitted_capabilities function and use
it in filecap"), breaking our usage of it. It's obvious that it's not
supposed to be used programmatically given the awful sed'ing we were
already doing. It doesn't seem like there was a compelling reason why it
was added either (bug #454908), so let's just get rid of it.
At the same time, fix the dependency on sys-libs/libcap by moving it to
RDEPEND, as dependencies in DEPEND/BDEPEND are not guaranteed to exist
during pkg_postinst() when this eclass is intended to run.
Signed-off-by: Matt Turner <mattst88@gentoo.org>