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Problem: documentation is out of date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
Problem: man page example code was truncated at any '@'

Solution: correctly end only for defined tags (@discuss, @end).
Generated documentation
Merge pull request #803 from hintjens/master

Problem: man page example code was truncated at any '@'
Problem: some dangling use of deprecated methods

Solution: replace with un-deprecated usage.
Merge pull request #804 from hintjens/master

Small cleanups
Problem: list and hash container APIs are messed up

There are a lot of good ideas in the new API yet the results are a
mishmash of old and new, without a clear route to a nice clean API.
The zring class was an attempt to fix this, yet it made things more
complex, not simpler.

I'm going to do this in stages:

* Deprecate the v2 classes, using the same names. This does not
  break existing applications. I'll remove some of the new messy
  code from these classes in a second step.

* Create new classes called zlistx and zhashx which initially look
  just like the old ones. I'll clean these up separately.
Problem: zmsg_popint is not useful (any more)

The usecase I had for this has gone and it's unclear it serves any
purpose. It adds clutter to the API for no benefit.

Solution: remove it.
Problem: still using zlist internally in CZMQ

Solution: leave zlist_t in public API where it's used (e.g. in
zdir and zconfig. Internally, switch all use of zlist to zlistx
except in deprecated classes. Also, switch to zlistx in public
API for zhashx_keys.
Merge pull request #805 from hintjens/master

Problem: list and hash container APIs are messed up
Problem: zlist_sort is broken

Solution: fix it, this code seems to have at least two major errors
in the design, as well as being more complex than necessary. Yay
test cases!