dev-lang/php: call `eselect php cleanup` in pkg_postinst and pkg_postrm.

dev-lang/php: call `eselect php cleanup` in pkg_postinst and pkg_postrm.

We have two bugs (432962 and 572436) regarding stale eselect symlinks.

The first issue is that removal of an old slot does not update the
eselect-php symlinks to point to a newer slot. Thus, if a user
upgrades slots and depcleans the old one, his symlinks (and thus PHP)
are left broken until eselect-php is run manually. This is fixed by
running `eselect php cleanup` in pkg_postrm, since removal of the
old slot will trigger a cleanup (which updates the symlink).

The second issue is that disabling a SAPI would leave behind a broken
symlink. For example, if the "cgi" SAPI was once used but the user has
reinstalled PHP with USE="-cgi", then the old eselect-php symlink for
php-cgi would be left behind. This is fixed by running `eselect php
cleanup` in pkg_postinst, since that will be triggered after the
reinstall finishes, at which point the php-cgi symlink will be dead
and thus get removed.

Gentoo-Bug: 432962
Gentoo-Bug: 572436

Package-Manager: portage-2.2.26