Previously, the name 's' was used for the index of a spot on the board,
as well as for the value of a combo, and for a few other purposes. Use
different names and mark the spot indexes using a custom type.
No binary change.
The columns of the board are labeled from A to H and J to T, which makes
I5 or i5 an invalid coordinate. Previously, reading this invalid
coordinate from a file resulted in the string "<6" appearing in the move
log.
The 'i' was converted into the nonexistent column 20, and PT(20, 5) got
an out-of-bounds argument, resulting in spot 120. Converting this spot
back into coordinates resulted in PT(0, 6). The '<' comes from
'letters[0]'.
There are still parts of the code that use an indentation level of 4
instead of the usual 8. Fixing that right now would introduce more
unnatural line breaks, so defer that until later.
No binary change.
This merges in all such remaining changes from the Linux port of the
NetBSD games, except in hunt (where substantial changes from OpenBSD
need to be looked at).
Some such changes were previously covered in PRs bin/6041, bin/6146,
bin/6148, bin/6150, bin/6151, bin/6580, bin/6660, bin/7993, bin/7994,
bin/8039, bin/8057 and bin/8093.
rillig