VS2013 debug build crashes compiler

[davidgyates]

I realise it's a historic compiler, clinging on for a last few months of support, but some of us still constrained by these things.

#define JSONCPP_VERSION_STRING "1.8.4"

with the debug build (release is ok) failing with:

error MSB6006: "CL.exe" exited with code -1073740940

Completely repeatable, and with an older version of jsoncpp (1.6.2) working ok.