nvidia-detect: add support for RHEL 7

Add detection of RHEL 7

Signed-off-by: Philip J Perry <phil@elrepo.org>
nvidia-detect: bump release to 331.79

Signed-off-by: Philip J Perry <phil@elrepo.org>
nvidia-detect: fix Xorg detection

Fix secondary Xorg detection.

Signed-off-by: Philip J Perry <phil@elrepo.org>
nvidia-detect: fix Xorg detection

Signed-off-by: Philip J Perry <phil@elrepo.org>