x11-wm/compiz: Clean up port's makefile

• Add modesetting to the drivers whitelist
• Use upstream name xfwm4 instead of xfwm to properly fall back
• Remove reference to former option GNOME
• Simplify option DBUS
• Add missing dependencies
• Add LICENSE
• Add USES=gnome, USES=gl and USE_GL=gl
• Reorder the variables to pet portlint
• Regenerate patch files to pet portlint

Metacity migrated to GTK+ 3 while Compiz still uses GTK+ 2. This
incompatibility was left unseen at make time because of a reference to
former option GNOME in an assertion which resulted in METACITY being always
disabled.

Committer's changes:

• Remove broken option METACITY
• Further lint the makefile

PR: 230894
Submitted by: Samy Mahmoudi <samy.mahmoudi@gmail.com>
Reviewed by: mat
Approved by: portmgr (maintainer timeout: > 14 days)
Differential Revision: https://reviews.freebsd.org/D19467