Log Message:
Configure with --enable-xplugin-dock-support to fix build on 64-bit-only
macOS. In exchange for avoiding the use of the bundled i386 binary blob,
this drops compatibility with older macOS (by requiring a newer API in
the system libXplugin). In case this had been building for anyone on
semi-recent macOS, bump PKGREVISION.

Addresses pkg/55880.