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
cmake: fix packaging categories to use runtime vs. core