Added a bunch of information to the near bottom of HOWTO.INSTALL
on calc Makefiles. This information discusses the various
Makefiles found in the calc source.
Added comments in various calc Makefiles about their origin.
In particular, for Makefiles that are constructed such as
Makefile.simple, custom/Makefile and custom/Makefile.simple
there are comments about how they were made.
For all calc Makefiles, including those in sub-directories,
near the top there is now a line of the form:
# SRC: ... some message about the origin ...
Some folks might think: “you still use RCS”?!? And we will say,
hey, at least we switched from SCCS to RCS back in … I think it was
around 1994 ... at least we are keeping up! :-) :-) :-)
Logs say that SCCS version 18 became RCS version 19 on 1994 March 18.
RCS served us well. But now it is time to move on. And so we are
switching to git.
Calc releases produce a lot of file changes. In the 125 releases
of calc since 1996, when I started managing calc releases, there
have been 15473 file mods!
