x11/libXau: update to 1.0.11

Remove GNU_CONFIGURE_MANPREFIX, add TEST_TARGET

Changes: https://gitlab.freedesktop.org/xorg/lib/libxau/-/compare/libXau-1.0.9...libXau-1.0.11
Reviewed by: diizzy, jbeich
Tested by: arrowd
Pull Request: https://github.com/freebsd/freebsd-ports/pull/273
Sponsored by: Serenity Cybersecurity, LLC