* Enable MSVC builds of Mono w/ ENABLE_NETCORE
* Fix non-netcore build
* Move the ENABLE_NETCORE definition to config.h where it belongs
* Replace .def with linker #pragmas
* TARGET_WIN32 -> HOST_WIN32 && HOST_X86
* Pick up MONO_ENABLE_NETCORE from cygconfig.h
* Make `./configure --with-core=only` MSVC builds working
* Include netcore sources unconditionally, move the condition into the .c file
* Fix MSVC C++ netcore build on Win32