Bug#749224: libgl1-mesa-dev: excessive dependencies when using proprietary nvidia driver

[Oswald Buddenhagen <oswald.buddenhagen@gmx.de>]

Package: libgl1-mesa-dev
Version: 9.2.2-1
Severity: normal

some years ago, nvidia said that people should compile applications
against the official GL headers, and debian followed suit, eliminating
the nvidia-glx-dev package, leaving mesa as the only libgl-dev provider.

however, the libgl1-mesa-dev package of course depends on
libgl1-mesa-glx, which pulls in the whole mesa stack including llvm.
that's tens of megabytes of dead packages on a system that does not use
mesa.

i suggest to rectify the situation by splitting out a
libgl1-mesa-minimal-dev package that provides the portable gl headers
and making that a libgl-dev provider. the package should only depend
on the virtual libgl1 package.

in the next step, packages which explicitly depend on libgl1-mesa-dev
(e.g. libcairo2-dev, which made me notice the problem to start with)
should be adjusted accordingly.