cJSONUtils: add decode_array_index_from_pointer as common helper function
cJSONUtils: add decode_array_index_from_pointer as common helper function

DaveGamble/cJSON,FSMaxB/cJSON,DaveGamble/cJSON,DaveGamble/cJSON,FSMaxB/cJSON,FSMaxB/cJSON,DaveGamble/cJSON,FSMaxB/cJSON,FSMaxB/cJSON