testsuite --recheck

[Ralf Wildenhues]

`testsuite --recheck' should probably restore variable settings from
the previous command line, similar to `config.status --recheck'.
Doing that right would require storing command line arguments in a
unambiguously quoted way in the testsuite.log file, to take care of
special characters, multiple adjacent whitespace and newlines etc.
Arguments after --recheck could still override the previous ones.

Nothing to hold up 2.66, but I might look into it eventually.

Cheers,
Ralf