crfsuite can't be built with msvc < 2015 about crfsuite

[tavianator]

What from #44 isn't supported by old MSVC? I'm guessing the PRI* macros? That could be worked around with something like

#ifndef PRIu32
#  define PRIu32 "u"
#endif

#ifndef PRIX32
#  define PRIX32 "X"
#endif

[kmike]

inttypes.h is not available in earlier MSVC; @fgregg worked around this for python-crfsuite by bundling this header (scrapinghub/python-crfsuite#34).

[tavianator]

Okay, we could check the MSVC version before #includeing <inttypes.h> and fall back on the manual #defines if it's too old. Not a Windows user though so I don't know how to write the correct version check or test it.