general compile error and warning fixes

[zeromus]

. fix a bunch of missing string and stdio headers (really weird that these crept into the code...?)
. typo amalgated -> amalgamated
. add #if JSON_USE_EXCEPTION guard around exception-throwing code
. change format string "%%.%dg" to "%%.%ug" for an unsigned int

[cdunn2001]

Minimally, wouldn't these have to be cstring and cstdio for strict compatibility with modern compilers?

Adding headers is fine. But could you tell us where this was failing to compile?

[zeromus]

Beats me. I dont use modern compilers or know anything about them. This was failing on visual c++ 2010.

[cdunn2001]

I'm not sure we can continue to support VS2010 for the master branch. 0.y.z will work fine.

But could you try #include <cstdio> and #include <cstring> in VS2010, and if it works, push that to this branch to update this pull-request?

[zeromus]

Ahh sorry I was mistaken. It wasn't VS2010, it was a ghetto version of ARMCC I have to use. Each of the files I added stdio.h or string.h to already had <cstring> and<cstdio> in it, and it wasn't sufficient--so your test is already done.

I noticed this snippet in one place (and snippets like it in many other places)

#if defined(__QNXNTO__)
#define sscanf std::sscanf
#endif`

This is representative of another solution to the actual problem I had (symbols like sscanf being undeclared, being in the std:: namespace instead). So, it seems you've dealt with this problem before.

Since I don't know anything about compilers from the present or the future (it's all the same to a guy stuck in the past) all I can do is naively google up things like http://en.cppreference.com/w/cpp/io/c/sscanf which seems to say those functions belong in std:: namespace indeed and assume your great modern compilers which support them without the std:: qualifier are leading you astray

I'll let you think on this a while before I do any reverting. I can't competently suggest anything, but can incompetently suggest you sprinkle the code with std:: liberally if you want to be standards-compliant with c++29 or whatever you're targeting. For instance, I fixed json_writer.cpp in a different way by adding six std::

[cdunn2001]

your great modern compilers which support them without the std:: qualifier are leading you astray

Some older compilers have problems with std:: sometimes, and sscanf in particular can be available in weird ways. We'll be standards compliant in 2.0, but for now it's helpful to some users if we avoid being too strict.

I'll let you think on this a while before I do any reverting.

Don't revert. But can you wrap the new include lines in and ifdef for your compiler? IIRC, some modern compilers actually do not include the old headers, or consider them a compiler warning (which becomes an error with -Werror).

For instance, I fixed json_writer.cpp in a different way by adding six std::

Could you show us where? We can't add that on 0.y.z, but on master I think that would be fine.

[cdunn2001]

Not sure about this anymore. Rebase and reopen if important.