Added gsl script to generate new class.
Merge pull request #747 from lovmoen/master

Problem: Creating a new class involves writing a lot of boilerplate code.
Problem: zsock_recv 'm' assumes initialized message

This is inconsistent with all other picture formats and leads to
surprising code.

Solution: always initialize message before reading off socket.

If we need an "append to message" picture that should be a special
case, e.g. using 'M' as picture.
Renamed zbase64 to zarmour.
Merge pull request #748 from lovmoen/master

Renamed zbase64 to zarmour.
Merge pull request #749 from hintjens/master

Problem: zsock_recv 'm' assumes initialized message
Moved zclass packaging to non-generated files.
Merge pull request #750 from lovmoen/master

Moved zclass packaging to non-generated files.
Fix compilation error

This issue was introduced with PR #747, which has forgotten to also add
list 'src' part of SUBDIRS.

Closes zeromq/czmq#751
Corrected some inaccuracies in zclass_example.xml documentation.
Updated zarmour.xml to reference correct script name.
Merge remote-tracking branch 'upstream/master'
Merge pull request #753 from lovmoen/master

Fixed some inaccuracies in zclass_example docs.
Merge pull request #752 from aquette/fix_compilation

Fix compilation error
Problem: code for zclock_mono is slightly too complex

Solution: refactor functions that are used only once, to make the
code easier to reuse.
Problem: need a microsecond monotonic clock

This is for performance measurements where milliseconds don't cut it.

Solution: add zclock_usec() as alternative to zclock_mono().
Fixed error for zclock_usecs prototype
Removed labs area

Fixes #757

Note, if anyone wants this area for development the cleaner solution
is to create a separate zlabs project under the ZeroMQ organization.

Having this in CZMQ isn't worth the extra pain of carrying it around
in build files, documentation, etc.
Updated generated classes (zproto updates)
Problem: long extension for Makefile supplement is surprising

We don't use long extensions anywhere else and this is surprising and
clumsy IMO. I don't know if there's a standard for this.

Solution: use a short extension (.ams).
Problem: proxy switch code isn't minimal

Solution: simplify it a little more.