Fix low-hanging gotos
Fix gotos that were simple replacements of break/continue/do-while/etc.
The gotos that are remaining are either multi-level breaks, other more
complex flow control, or in files I didn't bother to touch. (I didn't
bother with the multitude in apps/pilot/, as many of those are in
"private" applications, and some numeric/ files, as those look
to be straight transliterations of external code.)
All tests pass on my machine.