dev-lang/scala: Bump to 2.12.10

dev-lang/scala: Bump to 2.12.10

Thanks to toralf for reporting bug #623824, fixed with EAPI=7.

Thanks to Till Schafer for reporting bug #662184, fixed with:
use doc && einstalldocs

Thanks to Gentookh for reporting, fixed by only calling
check-reqs functions if ! use binary

Closes: https://bugs.gentoo.org/show_bug.cgi?id=623824
Closes: https://bugs.gentoo.org/show_bug.cgi?id=662184
Closes: https://bugs.gentoo.org/show_bug.cgi?id=617586
Package-Manager: Portage-2.3.84, Repoman-2.3.20
Signed-off-by: Mark Wright <gienah@gentoo.org>