AAS_LoadAASLump will return 0/NULL in an error case. However it will also
return the input buffer pointer if length is 0, and the input buffer pointer
may be 0/NULL in the case where AAS_LoadAASLump is meant to allocate memory.
This means that it can return 0/NULL in a perfectly legal case where the lump
length is 0. Since AAS_LoadAASFile inteprets this as a fatal error, that's
bad.
I'm not sure how to best disambiguate this, but a low-touch fix is for the
caller of AAS_LoadAASLump to be OK with a returned NULL pointer if the lump
length is 0.
Also: added a missing break statement to avoid a spurious "don't know what to
do" message when using the aasinfo switch.
The settings in cfgq3.c had diverged from the actual fields and defaults in
these ways:
- extra field phys_maxacceleration
- missing fields phys_walkaccelerate, phys_swimaccelerate, rs_maxfallheight
- different defaults for phys_airaccelerate, phys_maxstep, phys_maxwaterjump
Also the code in aas_cfg.[ch] for reading the settings was missing
rs_maxfallheight.
It's brittle to require multiple different files to agree on these fields, but
rather than fix that issue this is just a band-aid to bring things back into
alignment so that custom configs based on the example file can be used again.
