dev-lang/php: new revisions that install the "phar" executable

dev-lang/php: new revisions that install the "phar" executable

PHP supports installing a "phar" executable that simplifies creating
and extracting phar archives. This commit does so when USE=phar is
set. A forthcoming release of eselect-php will allow users to switch
between the different versions of the command.

While we're making revisions, the virtual/libffi dependency was
replaced by its sole provider, dev-libs/libffi.

Bug: https://bugs.gentoo.org/707876
Package-Manager: Portage-2.3.84, Repoman-2.3.20
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>