Push USES=pkgconfig to the global level instead just contingent on the
VKD3D option.

This makes a real difference for the GNUTLS option (on by default) and
others. Accordingly bump PORTREVISION.

Reported by: Benny Goemans <benny.goemans@belgacom.net>
MFH: 2020Q2 (blanket: missing dependency)