Errored: OpenSmalltalk/opensmalltalk-vm#1587 (WIN64_UNICODE - 5f71fce)

Handle both an ASCII (UTF8) and a WIDE (UTF16) version of image/vm name/path

Note:
the Microsoft windows API mostly uses the W version (for enabling internationalized image name/path)
the image uses UTF8 encoded bytes string for communication with the VM (this is best for compatibility with Unix/Mac)
The idea here is that the implementation maintains both versions of the UTF8 and UTF16 path/name

The appropriate macro returning a TCHAR * are also provided.
This is in order to support the generic version using TCHAR, which are normally used to ease transition to UNICODE.

Note about string length:
No effort has been made so far to support long path names for image and VM.
The path is limited to MAX_PATH in UTF16.
UTF8 can eventually consume more characters than UTF16 (not necessarily more bytes).
Thus, the ASCII version has been made longer (MAX_PATH_UTF8) in order to avoid an even more restrictive limit.