parser: use PyInt_FromSsize_t in index_stats
Eliminates
mercurial/parsers.c(515) : warning C4244: 'function' : conversion from
'Py_ssize_t' to 'long', possible loss of data
mercurial/parsers.c(520) : warning C4244: 'function' : conversion from
'Py_ssize_t' to 'long', possible loss of data
mercurial/parsers.c(521) : warning C4244: 'function' : conversion from
'Py_ssize_t' to 'long', possible loss of data
when compiling for Windows x64 target using the Microsoft compiler.
PyInt_FromSsize_t does not exist for Python 2.4 and earlier, so we define a
fallback in util.h to use PyInt_FromLong when compiling for Python 2.4.