VS2015 fixes

[0blu]

Fixes the compilation on VS14 / 2015.

[0blu]

There are also some warnings when converting from BOOL (aka int) to bool.
Which could be solved with != 0 check. (e.g. return _isatty(fd) != 0;)

[jeremy-rifkin]

Thanks so much for doing this! I wish it were easier for me to test older versions of compilers in CI to prevent regressions. I'll have to look into doing so later.

[jeremy-rifkin]

Thank you so much for taking the time to do this and working through the review comments! Looks good to me!