Bug#630710: please add Breaks: libgl1-nvidia-alternatives (<= 275.09.07-1)

[John Feuerstein <john@feurix.com>]

The libgl1-mesa-glx with Breaks: libgl1-nvidia-alternatives results in
problems for nvidia users:

Since packages like xorg, x11-utils, ... directly depend on
"libgl1-mesa-glx | libgl1", users are forced to uninstall them as well
as higher level packages depending on them due to nvidia-glx.

For example: Install metapackage xorg on current vanilla sid. Then try
to install nvidia-glx, which will result in this conflict.

Is there something I'm missing? Looks like there are some libgl1*
packages which are not ready for this.