This was not likely an error-free change. Where you see problems
please correct them. This went through a fairly tedious audit
before committing, but comments might have been changed incorrectly,
not changed at all, etc.
Swift SVN r7631
Now that we don't have formatForPrinting anymore, a terser name for
debugFormat makes more sense. Also, the new name isn't freighted with
so much implication about the end-user's activity.
Swift SVN r7256
Jordan pointed out that we already have these multi-parameter
format(...) functions that also return Streamables; it doesn't make
much sense to spell them differently.
Swift SVN r7255
