Cosmetic whitespace fixes.
Problem: zring is leaking memory for non-obvious reasons

Solution: this class is complex and pointless and solving no
agreed issue except "we lack a pointless and complex container".

Removed.
Problem: zmsg test is leaking memory

Solution: destroy stuff you create.
Problem: zrex does an unnecessary malloc in zrex_matches

Solution: don't reallocate hit_set unless needed.
Problem: zgossip was leaking memory on longstrings

Solution: fixed in zproto, and regenerated here.
Problem: project files still referred to zring

Solution: regenerate them.
Problem: czmq_selftest was mostly commented out.

(I was testing zgossip and forgot to revert the comments.)

Solution: revert the comments.
Generated documentation
Problem: documentation is out of date

Solution: we can rebuild it!
Merge pull request #802 from hintjens/master

Removed zring, fixed memory leaks