Change OpenAL distance model from AL_INVERSE_DISTANCE to
AL_INVERSE_DISTANCE_CLAMPED to avoid excessive volume when very close
to the sound location, for example MTG doors, and MTG fire sounds which
are combined at an average position and often located in air nodes.
Because AL_REFERENCE_DISTANCE has been reduced to 1 node (the distance
under which gain is clamped), multiply volume by the same factor to keep
sound gains the same as before, since the gain is calculated as:
gain = (AL_REFERENCE_DISTANCE / distance)
In createPlayingSoundAt(), AL_ROLLOFF_FACTOR is not set, so it has
the default value of 1.0, this makes the equation of the currently
used AL_EXPONENT_DISTANCE distance model identical to the equation
of the simpler AL_INVERSE_DISTANCE distance model.
Using AL_INVERSE_DISTANCE means an exponent is not processed,
exponents are quite intensive to process.
There is no change in sound attenuation behaviour.
The commented-out AL_ROLLOFF_FACTOR value is removed as it would
now have a different effect if used.
* Remove trailing lines from src/sound_openal.cpp
* Don't do a horribly ugly copy of the file's path, allocating and deallocating a
10 kb buffer in the process. This copy was needed for backwards compatibility
with libvorbis 1.3.1 and earlier, as the removed comment explains.
However, even Ubuntu precise has 1.3.2 already. Dropping support and sparing
the ugly copy can therefore be considered safe.
* Actually load sounds from the memory, not caching them at the disk first,
removing the old hack. This is the main motivation for the commit.
