Log Message:
frotz: Update to 2.52

Frotz 2.52 was released on Sunday May 10, 2020.

This is a minor release focusing on minor enhancements and bug fixes.

NEW FEATURES

- Partial support for new @set_true_colour opcode.  Works for SDL.
  Doesn't work all the way for curses.  Not in scope for dumb interface.

BUG FIXES

- Reworked Makefiles to better handle library detection, particularly
  for macOS.

- Fixed rendering of non-paletted PNG images.  Affected only non-Infocom
  V6 games.

- Rolled back idiosyncrasy fix for Cutthroats and changed over to the
  quick-and-dirty 24-to-12 conversion used by Infocom as this is how the
  Imps expected an interpreter to behave.

- Fixed broken handling of game paths set in environmental variables and
  in config files.

- Fixed slightly broken parsing of .sfrotzrc.

- Fixed behavior of command line processing inconsistent between the
  different user interfaces.

- Assorted source code formatting fixes.