Zap _THIS_PORT helper for printf("%n") tracking in ports land

Zap _THIS_PORT helper for printf("%n") tracking in ports land

This hack isn't very useful now that libc aborts on printf("%n") calls,
it's expected that the resulting error would lead to a build
failure, and that the coredump along with the syslog message should be
enough to find the culprit.

Hinted by naddy@ and prodded by deraadt@