The port will switch to the newer version if hw context is available in the
i915kms driver.

- Get ride of WITH_NEW_XORG.
- Use @comment in plist to ignore unwanted files in the stagedir, instead of
  trying to remove them in post-install.
- Bump portrevision of 9.1.7 due to dependency changes.
- Drop :keepla from USES=libtool.
- Drop @dirrm[try] from plists
- Give dri propper options, with pkg-help for additional information.
- Make separate plist for dri for the different versions, the combined plist
  was headache inducing.
- Add "workaround" patches to allow clang to build the dri port on i386 [1].
  USE_GCC is now only needed for 8.x.
- Add gbm port and USE_GL switch for it.

PR:		192286 [1]
Submitted by:	Carlos Jacobo Puga Medina [1]
Approved by:	portmgr (bapt@)
In collaberation with:	dumbbell@
Obtained from:	xorg-dev