MDEV-10411 Providing compatibility for basic PL/SQL constructs

Part 9: EXCEPTION handlers

- Adding exception handler syntax:
  WHEN exception_name THEN statement
- Adding EXCEPTION section intoi the top BEGIN..END SP block.
  Note, currently EXCEPTION goes in the beginning of the top BEGIN..END
  SP block.

TODO:
- add EXCEPTION section into inner blocks
- move EXCEPTION to the end of the block

mysql-test/suite/compat/oracle/r/sp.result

@@ -350,3 +350,23 @@ i
 4
 i
 3
+# Testing exceptions
+CREATE TABLE t1 (c1 INT);
+CREATE PROCEDURE sp1 (p1 IN VARCHAR2(20), p2 OUT VARCHAR2(30))
+IS
+v1 INT;
+BEGIN
+EXCEPTION WHEN NOT FOUND THEN
+BEGIN
+p2 := 'def';
+END;
+SELECT c1 INTO v1 FROM t1;
+p2 := p1;
+END;
+/
+CALL sp1('abc', @a);
+SELECT @a;
+@a
+def
+DROP PROCEDURE sp1;
+DROP TABLE t1;