Adding JSON_C_TO_STRING_PRETTY_TAB flag

- Tabs are easier to read for tired eyes and editor adjustable

json_object.h

@@ -50,6 +50,14 @@ extern "C" {
  * for an example of the format.
  */
 #define JSON_C_TO_STRING_PRETTY     (1<<1)
+/**
+ * A flag for the json_object_to_json_string_ext() and
+ * json_object_to_file_ext() functions which causes
+ * the output to be formatted.
+ *
+ * Instead of a "Two Space Tab" this gives a single tab character.
+ */
+#define JSON_C_TO_STRING_PRETTY_TAB (1<<3)
 /**
  * A flag to drop trailing zero for float values
  */