* lib/check-regexprops.sh: New test. Run regexprops as a check,
and compare its output against the contents of doc/regexprops.texi.
If there is a mismatch for regexprops.texi, save the correct version.
* lib/Makefile.am: Run check-regexprops.sh for 'make check'.
* doc/Makefile.am: don't clean regexprops.texi, and don't generate
it automatically.
* doc/regexprops.texi: add into source control.
it automatically.
* doc/.gitignore: don't ignore regexprops.texi