* added global functions that check whether FMod and OpenAL are present, without initializing the sound backend.
* make sound init code more fault tolerant. It will now try to switch between FMod and OpenAL if the currently active one cannot be found but the other one can.
* added 'ifoption' checks for sound backend to menu code.
* only show sound backends which are present and hide the options for the ones which are not.
This required the addition of a few exception handlers so to avoid #ifdef overuse I also added some #defines for non-Windows systems that allow using __try and __except directly in the code without #ifdef'ing them out.
UpdateSounds will not be called during screen wipes and the entire setup of this function suggests that this is not advisable at all.
The OpenAL stream updates were done deep inside this function implicitly.
This caused music to stop while a wipe was in progress. So in order to allow uninterrupted music playback during screen wipes the music updates need to be handled separately from sound updates and be called both in the main loop and the wipe loop.
I think that the OpenAL music updating should be offloaded to a separate thread but at least it's working now without causing interruptions during wipes.
- Viewheight change was delayed: Viewheight must be copied to player
structure as well as the PlayerPawn. Not sure if should actually use
deltaviewheight to spread the change out over a few tics instead of
being instant.
- Viewheight not preserved when travelling: player->viewheight must be
restored from pawn->ViewHeight, because the temporary player set it back
to the default viewheight.
- If palette index 255 happens to be white (e.g. as in Hexen), trying to
use white with DTA_FillColor would treat it as if you had never passed
it to DrawTexture().
- S_PrecacheLevel() must also mark currently playing sounds as
used. If we don't, the sound could be unloaded and the underlying
channel stopped without triggering a channel callback. That would leave
the code in s_sound.cpp thinking the sound is still playing even though
it isn't.
- Added an invalid channel check to FMODSoundRenderer::StopChannel() so
that orphan channels passed to it will be returned at least when
S_StopAllChannels() is called.
- OpenAL never actualy worked properly and was removed in later FMODs.
- Sound Manager was deprecated by Apple long ago and is not supported for
64-bit applications. It was also removed in later FMODs.
