Fix 'SHOW CREATE FUNCTION' to say 'FUNCTION' in its error message. (Bug #6338)

sql/sql_parse.cc:
  Fix SP_COM_STRING() macro for 'SHOW CREATE FUNCTION' case
mysql-test/r/sp-error.result:
  results for SHOW CREATE FUNCTION test
mysql-test/t/sp-error.test:
  test SHOW CREATE FUNCTION

mysql-test/r/sp-error.result

@@ -47,6 +47,8 @@ Warnings:
 Note	1305	PROCEDURE foo does not exist
 show create procedure foo|
 ERROR 42000: PROCEDURE foo does not exist
+show create function foo|
+ERROR 42000: FUNCTION foo does not exist
 create procedure foo()
 foo: loop
 leave bar;

mysql-test/t/sp-error.test

@@ -81,6 +81,8 @@ call foo()|
 drop procedure if exists foo|
 --error 1305
 show create procedure foo|
+--error 1305
+show create function foo|
 
 # LEAVE/ITERATE/GOTO with no match
 --error 1308

sql/sql_parse.cc

@@ -52,6 +52,7 @@
 #define SP_COM_STRING(LP) \
   ((LP)->sql_command == SQLCOM_CREATE_SPFUNCTION || \
    (LP)->sql_command == SQLCOM_ALTER_FUNCTION || \
+   (LP)->sql_command == SQLCOM_SHOW_CREATE_FUNC || \
    (LP)->sql_command == SQLCOM_DROP_FUNCTION ? \
    "FUNCTION" : "PROCEDURE")