update fields in the example custom config file

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.

Testing: just generating aas for jlctf3 with and without custom configs, seeing
changes in the reported stats, and checking that they were playable.