Make use of MSVC specific macros for format specifiers

[tbeu]

• Where inttypes.h is not availabale for VS<=2012 the MSVC specific macros still can be used.
• Tested with VS2010.
• See Fixed #255. MSVC2012(_MSC_VER=1700) doesn't have inttypes.h. #257

[redboltz]

Hi @tbeu, thank you for sending the PR. I don't get the point yet.

Here is my observation:

1. MSVC (<=2012) doesn't have inttypes.h
2. The macros such as PRIu64 are defined in inttypes.h
3. Hence the macros are not defined in MSVC (<=2012).

Is that correct?

So I wrote some workaround codes in objectc.c

https://github.com/msgpack/msgpack-c/blob/master/src/objectc.c#L127

I assume that if the macros are not provided, fprintf doesn't support the formats corresponding to the macros. If my assumption is correct, even if we define the macros by ourselves, fprintf doesn't recognize the format.

Could you tell me your idea?

[tbeu]

Yes, correct, but MSVC has special format prefixes I64 that can be used instead. This way the (limited) workaround is not used.

[redboltz]

Aha, I understand now. The format strings that you defined are MSVC extension. I will merge the PR soon.

[tbeu]

Thanks!