Avoid useless malloc/free traffic around getFormattedTypeName().
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.