remove dependency on librt on windows
Rename UA_NodeId.namespace to UA_NodeId.ns.
C++ compilers and syntax tools complain about variables called namespace.

Add WIN32 flag. Use MSVC flag for Visual Studio only code.
WIN32 code is also used by MinGW.
Merge branch 'master' of https://github.com/acplt/open62541

Conflicts:
	src/ua_types.c