Bug #21772: can not name a column 'upgrade' when create a table in version 5.0.24

Upgrade was a reserved word. Unreserve UPGRADE so it can be used in unquoted identifiers.

mysql-test/r/create.result

@@ -773,3 +773,5 @@ Warnings:
 Warning	1071	Specified key was too long; max key length is 765 bytes
 insert into t1 values('aaa');
 drop table t1;
+create table t1 (upgrade int);
+drop table t1;

mysql-test/t/create.test

@@ -674,4 +674,10 @@ create table t1(f1 varchar(800) binary not null, key(f1)) engine = innodb
 insert into t1 values('aaa');
 drop table t1;
 
+#
+# Bug#21772: can not name a column 'upgrade' when create a table
+#
+create table t1 (upgrade int);
+drop table t1;
+
 # End of 5.0 tests

sql/sql_yacc.yy

@@ -7555,6 +7555,7 @@ keyword:
 	| TRUNCATE_SYM		{}
 	| UNICODE_SYM		{}
         | XA_SYM                {}
+        | UPGRADE_SYM           {}
 	;
 
 /*