runtime: Windows MSVC compatibility fixes

* pmt_EXPORTS changed to gnuradio_runtime_EXPORTS
* WinSock2 used when appropriate
* Class definition syntax
* Explicit including of ICE_INCLUDE_DIR
runtime: add DLL resource file when using MSVC
Merge remote-tracking branch 'ncorgan/next_msvc_fixes' into next
digital: making virtual destructor for constellation class.
Merge branch 'maint'
Merge branch 'master' into next

Conflicts:
	gr-digital/include/digital_constellation.h
	gr-digital/lib/digital_constellation.cc
digital: making virtual desctructors for constellation and OFDM equalier base as parent classes.
build: cmake updates to find ICE when not installed in /usr.
cmake: fix packaging categories to use runtime vs. core
digital: cleaning up a few warnings.
Merge branch 'next' of gnuradio.org:gnuradio into next