We should use json_int_t instead of int, since this can be different
depending on platform. Also MSVC warns that this can cause "loss of
information" since it's converting long long to int.
The decimal point '.' is changed to locale's decimal point
before/after JSON conversion to make C standard library's
locale-specific string conversion functions work correctly.
All the tests now call setlocale(LC_ALL, "") on startup to use the
locale set in the environment.
Fixes GH-32.
