Fixups for building jsonsl for various platforms - Mac, ARM Linux, Windows VC8 to VC10

Hello,

I'm experimenting with using jsonsl for supporting JSON parsing in
a codebase called Regal - which is a cross-platform user-space
OpenGL layer.  There were some changes I needed to do for our
various automated builds, and to silence warnings.  For your
consideration to upstream.

- Nigel Stewart

https://github.com/p3/regal