In json code, clean up temp memory contexts after processing.

Craig Ringer.

src/backend/utils/adt/jsonfuncs.c

@@ -972,6 +972,8 @@ each_worker(PG_FUNCTION_ARGS, bool as_text)
 
 	pg_parse_json(lex, sem);
 
+	MemoryContextDelete(state->tmp_cxt); 
+
 	rsi->setResult = state->tuple_store;
 	rsi->setDesc = state->ret_tdesc;
 
@@ -1154,6 +1156,8 @@ elements_worker(PG_FUNCTION_ARGS, bool as_text)
 
 	pg_parse_json(lex, sem);
 
+	MemoryContextDelete(state->tmp_cxt); 
+
 	rsi->setResult = state->tuple_store;
 	rsi->setDesc = state->ret_tdesc;