libansilove: update to 1.2.4.

libansilove 1.2.4 (2020-06-21)

- Use size_t in for loops setting color palettes
- Remove unneeded gdImageFill() call when using Workbench mode
- Define _GNU_SOURCE in CMakeLists.txt to avoid cluttering source files
- Use size_t type for variables used to loop over arrays
- Separate RGB values for palettes, makes color allocation code more
  readable and efficient
- Move ADF color mapping array to config.h

(fcambus)