Add a json_c_version.h header (included from json.h), and several macros and functions for retrieving the json-c version at compile-time and run-time.

Makefile.am

@@ -21,6 +21,7 @@ libjson_cinclude_HEADERS = \
 	debug.h \
 	json.h \
 	json_config.h \
+	json_c_version.h \
 	json_inttypes.h \
 	json_object.h \
 	json_object_iterator.h \
@@ -48,6 +49,7 @@ endif
 libjson_c_la_SOURCES = \
 	arraylist.c \
 	debug.c \
+	json_c_version.c \
 	json_object.c \
 	json_object_iterator.c \
 	json_tokener.c \