[PATCH xserver] build: Enable vidmode independently from Xorg

[Adam Jackson]

On Fri, 2016-03-04 at 16:24 +0100, Rui Matos wrote:
> This allows building Xwayland without Xorg and still include the
> vidmode extension.
> 
> v2: Use PKG_CHECK_EXISTS instead of PKG_CHECK_MODULES

remote: I: patch #75875 updated using rev 40a164b8f4e720b0d6ebf228ee175eb397ffeec2.
remote: I: 1 patch(es) updated to state Accepted.
To ssh://git.freedesktop.org/git/xorg/xserver
   2be527b..40a164b  master -> master

- ajax