Added zbase64 documentation.
Merge pull request #746 from lovmoen/master

Problem: zbase64 documentation was missing
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.
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