v2.2.1 — CMake-based necpp v2.2.0 engine, build fixes

v2.2.1

Changes

• Build fixes for the CMake-based necpp (v2.2.0) submodule:
  • Exclude nec_wasm.cpp from the Python extension source glob (Emscripten-only; broke native builds).
  • necpp/build.sh: fix submodule init (--init), document the necpp_src symlink required by setup.py.
  • PyNEC/setup.py: remove dead necpp_src/win32/ include dir (gone in CMake necpp; config.h is now CMake-generated in build/).
  • MANIFEST.in: point config.h include at src/config.h.in (generated, not committed).
  • Fix stale config.h comments in both setup.py files.
• Version bump to 2.2.1.