Add the --version argument to the "pikchr" command-line tool.
Add the pikchr_version() API function that returns a string showing
the Pikchr version number and the date/time of the source code check-in.
Include the ISO timestamp of the source code check-in in a data-*
field of the <svg> element.
Add a new keyword "pikchr_date" to the language. This keyword acts
like a string literal that contains the check-in date of the source code.
So another way to find the specific version of Pikchr that is running is
to render a pikchr script like: "box pikchr_date fit;"
The pikchr.c and pikchr.h sources are build products. They were
formerly under source code management, for convenience. But as they now
contain version-dependent information (such as the source code check-in
timestamp) they are no longer versioned. You need to run the Makefile
to generate those files from canonical sources.
Add a version number (1.0 in this case) because
Homebrew requires all the software they deliver to
have a version number, and we want Pikchr to be
available via Homebrew.