Adjust yywrap macro for non-reentrant scanners for MSVC.

Adjust yywrap macro for non-reentrant scanners for MSVC.

The MSVC compiler complains if a macro is called with less arguments
than its definition provides for. flex generates a macro with one
argument for yywrap, but only supplies the argument for reentrant
scanners, so we remove the useless argument in the non-reentrant
case to silence the warning.