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.
Thanks to Basile Starynkevitch for the suggestion and initial patch.
Thanks to Jonathan Landis and Deron Meranda for showing how this can
be utilized for implementing secure memory operations.