json-cpp Code

Added missing includes for std::istream.

Thanks to Quentin Fiard for the report.

Fixed broken build on VS 2012

Fixed some snprintf-related build breakages in Visual Studio.

Updated two calls to sprintf that I missed in r269.

Replaced the complex implementation of valueToString(double).

The previous one was confusing and prone to buffer overflows, and didn't
work correctly with 16-decimal-digit numbers. The new one simply uses
snprintf with a standard format string.

The major change is that we don't always print a decimal point now.
Fortunately, JSON doesn't distinguish between integers and reals.

Added more floating point tests.

The first demonstrates a bug that I will soon fix.

Added further floating point tests.

Switched away from sprintf, which is prone to buffer overflows.

Most reasonable platforms have this function. If you're here because
this broke the build for you, consider adding an ifdef for your platform
and using sprintf there (but not on other platforms).

- CMake: added option to turn fail compilation if warning occurs, and warning level 4 with MSVC.
- Fixed some warnings

- disabled warning 4786 for VS6 caused by STL (identifier was truncated to '255' characters in the debug information)
- added batchbuild config for XP VM