json-cpp Code

fix stdexcept

https://sourceforge.net/p/jsoncpp/bugs/68/

Added an exit() to JSON_FAIL_MESSAGE to fix "no return" errors.

Got rid of several unnecessary includes of <iostream>.

Including <iostream> causes the file to be polluted with a static
initializer for the __ioinit symbol. This can harm binary startup time.
For more info, see here:

http://neugierig.org/software/chromium/notes/2011/08/static-initializers.html

Made JSON_USE_EXCEPTION's value in config.h a default that can be overridden.

This allows users to override it with their compiler invocation. For example:

g++ -D JSON_USE_EXCEPTION=0 ...

Added line breaks to make error messages easier to read.

Fixed a missing include error.

Centralized assertion macros and made them obey JSON_USE_EXCEPTION.