win32: close zmq-signaler-port-sync event object to avoid handle leak
eliminate code moved into zmq_utils.cpp
Fix inconsistently using #if or #ifdef instead of #if defined
First pass at getting cmake build to work with non-Windows systems.

Also start fixing MSVC build requiring cygwin
Make doc building option dependent on asciidoc being installed
Fix ZMQ_HAVE_UIO name
Generated header is not in ../src/
Install sources to a zmq prefix
Windows cmake build fixes
Fix NSIS installer errors, MinGW build.

The CPack NSIS installer was in a state where it would always give a
useless error. I think it was using stuff intended for running cpack
separately from cmake.
Fix cmake poller selection
Fix unused argument warnings
Fix -Wmissing-field-initializers
Fix -Wmismatched-tags
Fix some of the -Wshadows
Fix warnings with MinGW
Fix typos
Comments about ICC build failure with 12.x were crazy
Fix warnings with ICC / don't use -Wextra
Fix cmake build with sun studio