cext: fix warnings when building for py3 on Windows MSVC++ 14 now has standard int types that don't need to be redefined (I didn't go back to see when they came along since the build system wants either 2008 or 2015), but doesn't have ssize_t. The FILE pointer in posixfile is only used on python2.

cext: stop preprocessing a partial function call MSVC++ 14 yelled: mercurial/cext/revlog.c(1913): fatal error C1057: unexpected end of file in macro expansion At this point, the C extensions build (with warnings), and it dies in win32.py because the `_fields_` strings in the ctypes classes are being converted to bytes by the source translator.

py3: add b'' to some setup.py strings for Windows These were things found trying to do `make PYTHON="py -3" local`. The following is dumped out, before dying while compiling the C extensions: C:\Program Files\Python37\lib\site-packages\setuptools\dist.py:406: UserWarning: The version specified (b'4.7.1') is an invalid version, this may not work as expected with newer versions of setuptools, pip, and PyPI. Please see PEP 440 for more details. "details." % self.metadata.version running build_py byte-compiling .\mercurial\thirdparty\concurrent\futures\_base.py to _base.cpython-37.pyc File "mercurial\thirdparty\concurrent\futures\_base.py", line 416 raise exception_type, self._exception, self._traceback ^ SyntaxError: invalid syntax # skip-blame since these are just converting to bytes literals