Coverity complained that one caller of getFormattedTypeName() failed
to free the returned string.  Which is true, but rather than fixing
that one, let's get rid of this tedious and error-prone requirement.
Now that getFormattedTypeName() caches its result, strdup'ing that
result and expecting the caller to free it accomplishes little except
to waste cycles.  We do create a leak in the case where getTypes didn't
make a TypeInfo for the type, but that basically shouldn't ever happen.

Back-patch, as commit 6c450a861 was.  This isn't a particularly
interesting bug fix, but the API change seems like a hazard for
future back-patching activity if we don't back-patch it.