Now that you can specify negative indents in Halibut text mode, it's

Now that you can specify negative indents in Halibut text mode, it's
possible to specify an indent which is _overall_ negative, i.e.
intended to be off the left-hand side of the text file. There's no
nice way to handle this, but printing O(2^32) spaces in a while (n--)
loop is particularly bad. Fix the loop to read while (n-- > 0), so
that at least it doesn't get _that_ badly confused.

git-svn-id: svn://svn.tartarus.org/sgt/halibut@9491 cda61777-01e9-0310-a592-d414129be87e