Getting rid of qal functions

There is now a direct use of OpenAL, rather than indirect use of its
functions through pointers. Correct OAL related sources addition from
CMake.
al.h was still on CMake
Introducing 'al_strings'

New command 'al_strings' is the equivalent of 'gl_strings' for OpenAL
backend
Doing several OGG fixes

Proper inclusion of OGG/Vorbis support
ogg_enable = 1 by default