opal v2.0.3

The synthesis core is the same as 2.0.2. This release is the example player and the web
demo. OPAL_VERSION_PATCH is 3 so the tag, the CMake package, and the header agree.

Fixed

• HSC replay in format_hsc.c followed AdPlug's ChscPlayer. It now follows HSC-Tracker
  HSCOBJ 1.4 / HSCPLAY. Unmatched effects including 0x3n, 0x5n, 0x6n, and 0xDn
  set speed to n + 1. OPL register 08 is written 0x40 (NOTESEL), not 0x80 (CSW).
  Notes pack fnum, block, and key-on into one 16-bit word on A0/B0. 0x1n/0x2n slide
  that word's low byte by n + 1 with no carry into the block. 0xAn/0xBn/0xCn
  replace the level byte and drop the instrument KSL bits. An instrument-set with slide
  0 leaves the key off. Setting the same patch again is a no-op, so the channel is not
  keyed off. Out-of-range pattern indexes play empty rows. The 51st order slot is played.
  The KSL xor applies to the carrier always, and to the modulator only in additive mode.
  Instrument slide is the high nibble of byte 11.
• DRO register writes and IMF delay 0 return zero frames from step. The example player
  and the web callback then spun in while (wait == 0) on the audio thread. Each callback
  now caps consecutive zero-wait steps and yields, so a register dump cannot hang playback.

Changed

• An HSC order jump or end marker is a loop point, not the end of playback. The example
  CLI player keeps the same file going, so tracks such as Rocky Margarine run until you
  stop them. The web demo treats that edge as the end of the current file and starts the
  next track, wrapping the list, until Stop. DRO and IMF still end when the stream runs
  out.

Documentation

• README points at sehnsucht as the full-featured terminal player that uses the opal
  emulator, not the example C formats. The web demo plays the bundled tracks in order.
  Language bindings stay at 2.0.2-1, because the C API did not change.