Missing support for _MSC_VER 1900

[jwittner]

Project upgrades require a few changes:

• Update project intermediate directories to avoid warning about overlapping intermediate directories.
  • Pretty easy and I've already got this going.
• Update boost to 1.61.0
  • Also pretty easy and upgrading was as easy as adding the new version and updating the include directories. Currently I dropped all of boost in so I'll have to reduce to the necessities at some point.
• Security warnings about getenv
  • This is my current hurdle. I could just disable these, but that's weak sauce. Would use of _dupenv_s/free be ok? Or an attempt with a 1k stack buffer then fallback to _dupenv_s/free?

Things are building for me currently in Visual Studio 2015 Update 3, but I'd like to get the final warnings squared away and reduce boost before doing a PR.

[rashadkm]

Thanks for adding support for msvc2015!. This is a great addition to the list of supported compiler where msvc is the one that is behind.

regarding getenv, is there a better way other than _dupenv_s ?. I don't have a windows machine so cannot test it. how about GetEnvironmentVariable from https://msdn.microsoft.com/en-us/library/ms683188(VS.85).aspx

also I am not clear when you said dropped all of boost ?. is boost no more a dependency?

And finally PR is more than welcome. I would be happy to merge your changes.

[jwittner]

Digging into _dupeenv_s I'm now seeing that it's a MSFT extension to the crt, I thought before that it was standard. I'm thinking now to keep the implementation the same on all platforms I'll just drink the weak sauce and disable the security warning for the MSFT compiler. That ok?

Regarding boost, I was just saying that my current upgrade to the newest version of boost involved "dropping in" the entire boost library. That's overkill so I was going to reduce it to match just the dependencies already included from the older boost library.