375.20 long term release and libEGL glvnd implementation

[Andreas Beckmann]

Hi Luca,

you didn't get the alternative dependencies right ... but trying to fix
this, I noticed that it's already wrong here:

  libgl1-glvnd-nvidia-glx | libgl1-nvidia-glx,

because libgl1-glvnd-nvidia-glx is only the loader/interface, without
any implementation, while libgl1-nvidia-glx is an implementaiotion ...

OK, so we will get for libgl-* (and similarily for libegl-*):

  libgl1-nvidia-glvnd-glx | libgl1-nvidia-noglvnd-glx

dropping libgl1-nvidia-glx and adding these 2 new packages instead.

(libgl1-nvidia-noglvnd-glx is renamed from libgl1-nvidia-glx while
libgl1-nvidia-glvnd-glx is new with a
  Depends: libgl1-glvnd-glx | libgl1-glvnd-nvidia-glx, libglx-nvidia0
to pull in the loader interface *and* the implementation)


Andreas