This is the main bulk of this boolification work, but although it's
making the largest actual change, it should also be the least
disruptive to anyone interacting with this code base downstream of me,
because it doesn't modify any interface between modules: all the
inter-module APIs were updated one by one in the previous commits.
This just cleans up the code within each individual source file to use
bool in place of int where I think that makes things clearer.

This commit removes the old #defines of TRUE and FALSE from puzzles.h,
and does a mechanical search-and-replace throughout the code to
replace them with the C99 standard lowercase spellings.

Now the flag passed to edsf_merge to say whether two items are the
same or opposite is a bool, and so is the flag returned via a pointer
argument from edsf_canonify.

The latter requires client code to be updated to match (otherwise
you'll get a pointer type error), so I've done that update in Loopy,
which is edsf's only current in-tree client.

[originally from svn r8796]

any equivalence class is always the element with the smallest index.
This is slower (the previous behaviour, suggested by Jonas Koelker,
was to choose the new root element to maximise performance), but
still more than acceptably fast and more useful.

[originally from svn r8792]

[originally from svn r7326]

working around bugs in the Palm compiler and removing Palm-
incompatible diagnostics such as fprintf.

[originally from svn r6889]

source files from Mike rather than patches, and not adequately
checking the result...

[originally from svn r6882]
[r6780 == f05c25347d66821d928668a7e87dffbf3ffed027]
[r6880 == b9547673c6462bf73e642328300479df6df71d7b]

rise to a new Hard difficulty level.

[originally from svn r6880]

[originally from svn r6780]