We currently test setting a symbol with a value even if it didn't
originally had one and vice versa. So there's no need to have separate
lists of symbols to test with. Just test everything we want to test
with each symbol.
Normally a valueless symbol remains valueless and a symbol with a
value keeps having one. But just in case a symbol does get changed
from valueless to having a value, make sure there's a space between
the symbol and the value. And if a symbol gets changed from having a
value to valueless, strip trailing whitespace.
Add corresponding tests.
Also fix the case of a valueless symbol added with the set method,
which would have resulted in attempting to use None as a string. This
only happened with the Python API, not with the command line API.
Run config.py with various options and store the results in files.
This script also supports the now-removed config.pl.
This is a framework to run non-regression tests on config.py: run it
with the old version, run it with the new version, and compare the
output.
This is deliberately not a functional test suite so that we don't need
to maintain a set of known outputs. When something changes in
config.py (or config.h), run the script before, run it after, and
check manually whether any differences in the output are acceptable.
