Some MSVC-fixes

[maghoff]

Unfortunately, libjson does not compile with MS's C compiler :(

These commits fix some of the problems. Some of the changes, for example relating to signed vs unsigned, make sense independently of MSVC, I think.

With all these changes, it still won't work in MSVC, because it does not implement support for designated initializers for arrays :( This does not seem to be on the roadmap for MSVC either, unfortunately.

Even though it still won't work in MSVC, I find it valuable to deviate as little as possible from what works on the greatest amount of compilers. Pull what you feel like, and disregard the rest, no stress :)

If the actions_map could easily be initialized in an MSVC-friendly way, I would be very grateful. I'm a bit scared of that table myself, so I don't know quite where to start if I were to change it :) I've implemented initializing it at runtime as a test, and with that final change it works nicely in MSVC.

[vincenthz]

thanks you for the commits, I think that's useful to be able to compile under MSVC (although i would wish they would be more compliant with gcc ;)).

which part of the actions_map table MSVC is complaining about ? is it the function pointer or the array initilizer that it thinks is non-constant ?