Fixed BUG#8408: Stored procedure crash if function contains SHOW

We simply have to disallow any kind of result set being sent back
  from a function. Can't see any way to make that to work.


mysql-test/r/sp-error.result:
  New test case for BUG#8408.
mysql-test/t/sp-error.test:
  New test case for BUG#8408.
sql/item_func.cc:
  Disable result sets from functions but temporarily turning CLIENT_MULTI_RESULTS off.
sql/share/errmsg.txt:
  Added error message for statements not allowed in functions (detected during parsing).
sql/sql_yacc.yy:
  Don't allow result sets in functions.

mysql-test/r/sp-error.result

@@ -594,4 +594,52 @@ alter function bug7047;
 return 0;
 end|
 ERROR HY000: Can't drop or alter a FUNCTION from within another stored routine
+drop function if exists bug8408|
+drop procedure if exists bug8408|
+create function bug8408() returns int
+begin
+select * from t1;
+return 0;
+end|
+ERROR 0A000: Not allowed to return a result set from a function
+create function bug8408() returns int
+begin
+show warnings;
+return 0;
+end|
+ERROR 0A000: Not allowed to return a result set from a function
+create function bug8408(a int) returns int
+begin
+declare b int;
+select b;
+return b;
+end|
+ERROR 0A000: Not allowed to return a result set from a function
+create function bug8408() returns int
+begin
+call bug8408();
+return 0;
+end|
+create procedure bug8408()
+select * from t1|
+call bug8408()|
+val	x
+select bug8408()|
+ERROR 0A000: SELECT in a stored procedure must have INTO
+drop procedure bug8408|
+drop function bug8408|
+create function bug8408() returns int
+begin
+declare n int default 0;
+select count(*) into n from t1;
+return n;
+end|
+insert into t1 value (2, 2.7), (3, 3.14), (7, 7.0)|
+select *,bug8408() from t1|
+val	x	bug8408()
+2	2.7	3
+3	3.14	3
+7	7	3
+drop function bug8408|
+delete from t1|
 drop table t1|