p/primus: initial addition

Based on https://github.com/zhurikhin/primus/commit/5c4d51e with the following
changes:

- add new changelog entry with correct debian version.
- remove nvidia dependency from primus, the correct dependency will be pulled by
  bumblebee.
- Add primus-lib-dbg package containing debugging symbols.
- Make primus an "any" architecture, remove Multi-Arch mention
- add colon-paths.patch, do not always set nvidia path in
  ubuntu_libgl_path.patch so that it can work with fglrx/nouveau/radeon.
- remove fixup ugliness from rules, strip superfluous comments.
p/primus: add nvidia to LD_LIBRARY_PATH even if libGLa is empty

In addition, correct the default paths in order to not confuse the user.
p/primus: drop confusing quotes, fixed by upstream
p/primus: add missing $, fix nvidia ldpath

Reported by amonakov and Dmitry, PRIMUS_libGLa would expand to an empty
string, therefore always set PRIMUS_libGLa to nvidia if it was not set.
p/primus: remove colon path, added upstream
primus: Fixed compat for precise
primus: Fixed debhelpers for precise
Merge branch 'master' into primus-proposed

Update primus-proposed to latest master
raring/primus: New clean packaging attempt
raring/primus: One forgotten $LIB replacement
pq/primus: Added/updated buildscripts
Merge branch 'primus-proposed'
pqr/primus: Synced changelog timestamp