Fixed BUG#14233: Crash after tampering with the mysql.proc table

Post-review version. Some minor review fixes, but also changed the way
  some errors are handled: Don't return specific parse errors; instead
  always use the more general "table corrupt" error (amended accordingly).


mysql-test/r/sp-destruct.result:
  Updated results.
mysql-test/r/sp-error.result:
  Updated for fully qualified name in "no return" error message.
mysql-test/t/sp-destruct.test:
  Adopted the more consistent error handling for a corrupted mysql.proc table.
  (No more "parse error" et al).
sql/share/errmsg.txt:
  Changed ER_SP_PROC_TABLE_CORRUPT to be more explicit.
sql/sp.cc:
  Review fixes.
  Changed the handling of parse errors, and added the routine name to the "table corrupt" error message.
sql/sql_base.cc:
  Review changes: Change error tests and added comments.
sql/sql_parse.cc:
  Mored ER_SP_NORETURN test of functions to sql_yacc.yy for more general error handling.
sql/sql_yacc.yy:
  Mored ER_SP_NORETURN test of functions from sql_parse.cc for more general error handling.

mysql-test/r/sp-error.result

@@ -124,7 +124,7 @@ begin
 declare x int;
 set x = val+3;
 end|
-ERROR 42000: No RETURN found in FUNCTION f
+ERROR 42000: No RETURN found in FUNCTION test.f
 create function f(val int) returns int
 begin
 declare x int;