To deal with fools^Wpeople trying to keep really old systems alive,
create a proper framework for substitution functions, and make it
possible to deal with the lack of snprintf/vsnprintf in particular.
Add special operators to allow the use of floating-point constants in
contexts other than DW/DD/DQ/DT/DO.
As part of this checkin, make MAX_KEYWORD generated by tokhash.pl,
since it knows what all the keywords are so it can tell which one is
the longest.
Sort the dependency lists generated by "mkdep.pl", to make sure that
re-running "make alldeps" doesn't change anything unless there has
been real dependency changes. The previous version could produce
different output between runs and across platforms.
