Enable ILASM for *nix

Enable ILASM for *nix

This enables ILASM for x-platforms.
1. Added a bunch of warning disable options mostly due to this prebuilt asmparse.cpp
2. Create a separte entry point "main" to pass WCHAR arguments.
3. PDB (CorSymWriter) part is disabled.
4. Converting/embedding resource file to binary is disabled.
5. jkotas kindly provided a code for IsTextUnicode which is unavailable on CoreCLR.