emerge: add --autounmask-keep-keywords option (bug 622480)

The option prevents --autounmask from making changes to
package.accept_keywords. This option does not imply
--autounmask-keep-masks, so --autounmask is still allowed
to create package.unmask changes unless the
--autounmask-keep-masks is also specified.

X-Gentoo-bug: 622480
X-Gentoo-bug-url: https://bugs.gentoo.org/622480
Reviewed-by: Manuel RĂ¼ger <mrueg@gentoo.org>
4 files changed