MINOR: cfgcond: remerge all arguments into a single line

MINOR: cfgcond: remerge all arguments into a single line

Till now we were dealing with single-word expressions but in order to
extend the configuration condition language a bit more, we'll need to
support slightly more complex expressions involving operators, and we
must absolutely support spaces around them to keep them readable.

As all arguments are pointers to the same line with spaces replaced by
zeroes, we can trivially rebuild the whole line before calling the
condition evaluator, and remove the test for extraneous argument. This
is what this patch does.