Make real number encoding and decoding work under all locales

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.

test/bin/json_process.c

@@ -5,12 +5,20 @@
  * it under the terms of the MIT license. See LICENSE for details.
  */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
 #include <jansson.h>
 
+#if HAVE_LOCALE_H
+#include <locale.h>
+#endif
+
 static int getenv_int(const char *name)
 {
     char *value, *end;
@@ -55,6 +63,10 @@ int main(int argc, char *argv[])
     json_t *json;
     json_error_t error;
 
+#if HAVE_SETLOCALE
+    setlocale(LC_ALL, "");
+#endif
+
     if(argc != 1) {
         fprintf(stderr, "usage: %s\n", argv[0]);
         return 2;