Fixes #18.

These aren't needed anymore after Striker's patch to improve overall interpolation.

Fixes #20.

audiolib: fix crash when a configuration file contains mus_xmp_interpolation but multivoc isn't initialized when the cfg is parsed

We're explicitly using the functions that rely on the overflow detection functionality, so this will never be useful to us.

This also resets wavetype to FMT_UNKNOWN in MV_CleanupVoice(), and moves the resetting of a few structure members common to different voice types there.

(No difference with Duke.)

Add internal standardhalfheight and tilesizx

Fixes #17.

Probably actually fixes #4. Regardless, I want to note that this is really sub-optimal.

Fixes #2.

Fixes #3.

Fixes #4.

Fixes #1.

PACKED macro. This is more consistent with the current Duke3D codebase,
and further fixes build with older versions of MinGW GCC, in which
attribute packed is broken without specifying -mno-ms-bitfields.

SW 1.2 after minor adjustments. Originally recreated
for sw-src-and-build-addendum-20190129.7z.

and also as currently in use in EDuke32-OldMP.

the sync check on the slave side in Master/Slave mode.

Let's see if this is breaking anything.

Increase MAXINTERPOLATIONS from 1024 to MAXSPRITES.