The problem is that other threads might still be in mailbox::send() when
it is destroyed. So as a workaround, we just acquire the mutex in the
destructor. Therefore the running send will finish before the mailbox is
destroyed.

See also the fix for LIBZMQ-281 in zeromq2-x.
Signed-off-by: Mika Fischer <mika.fischer@zoopnet.de>

Update PGM with recent changes

Fixed CMake building after encoder/decoder changes

Fixed copyrights in sources

* Starting draft ZMTP/2.1 protocol (revision 2)
* Basis for adding security to the wire protocol
* Maintains backward compatibility

Copyrights had become ads for Sustrik's corporate sponsors, going against the original
agreement to share copyrights with the community (that agreement was: one line stating
iMatix copyright + one reference to AUTHORS file). The proliferation of corporate ads
is also unfair to the many individual authors. I've removed ALL corporate title from
the source files so the copyright statements can now be centralized in AUTHORS and
source files can be properly updated on an annual basis.

Adapted zmq_socket_monitor man page to new API.

Changed message structure for event notifications

Simplified zmq_event_t structure.

Simplified the zmq_event_t structure for easier access and better usability towards language bindings.

Fixed Linux compilation problem

remote_thr.cpp: port pthreads usage to win32 api

this follows what {local,remote}_lat.cpp and inproc_{thr,lat}.cpp do.

Windows: Fix rounding error in now_us. [Jira LIBZMQ-514]

Improve accuracy of time calculations and avoid division by zero when
ticksPerSecond.QuadPart < 1000000.

Improvements and fixes for performance of PUSH/PULL in local_thr and rem...

- option to set number of zmq threads on the command line for local_thr
- option to set number of zmq_threads and workers in remote_thr
- option to set SND/RCV buffer sizes on command line
- option to set whether to PUSH/PULL on command line
- option to set to use zmq_recv or zmq_msg for transfer on command line
- better timing function
- corrected and improved throughput reporting
- HWM and DELAY socket options

Fixed overflow in results calculation

Static Library Linking for Windows

+ ignore StaticRelease & StaticDebug intermediate files

- New ZMQ_STATIC flag to enable "libzmq.lib" Windows static library (or "libzmq_d.lib" in Debug mode).
- ZMQ_STATIC needs also to be defined by projects using static linking against "libzmq.lib"
- New StaticDebug & StaticRelease configurations for libzmq Win32 projects under MSVC 2008 & 2010
- Tested with Visual Studio 2008 Express under Windows 7, and Visual Studio 2010 Express under Windows 8.

Fixed module path with cmake < 2.8.3

Corrected linking error in MSVC 2010 build + perf/projects compilation