Add an X11 option to java/openjdk[78]

It defaults to on. Disabling it will remove X support from Java, and reduce
X-related dependencies.

PR: 210000
Reviewed by: brd
Approved by: brd (ports)
Approved by: glewis (maintainer timeout)
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D6698