* revise xmidi conversion:
- eliminates 2-pass conversion, does the job in 1-pass using realloc
- eliminates initXMI and does only xmi2midi by combining old initXMI+
  old xmi2midi.
- doing the above removes requesting a specific track. (see below.)
- adds support for multi-track xmi files by outputting type-2 (which
  needs implementing in wildmidi_lib.c properly) instead of type-0:
  if type-2 is implemented, then specific track requests can be done
  when calling wildmidi_lib functions instead of xmidi converters.
- removes 'fixing of broken midis' (ctx->fixed and its associated
  MovePatchVolAndPan procedure.)