Fix for bug #4492.

TIMESTAMP columns should be unsigned to preserve compatibility with 4.0
(Or else InnoDB will return different internal TIMESTAMP values when user upgrades to 4.1).

Altough this fix will introduce problems with early 4.1 -> 4.1 upgrades (tables with 
TIMESTAMP field should be reloaded using mysqldump) it will allow easy 4.0 -> 4.1 
upgrade (which is more important since 4.1 is still beta).

mysql-test/r/metadata.result

@@ -21,7 +21,7 @@ def	test	t1	t1	g	g	5	4	0	Y	32768	3	63
 def	test	t1	t1	h	h	0	7	0	Y	32768	4	63
 def	test	t1	t1	i	i	13	4	0	Y	32864	0	63
 def	test	t1	t1	j	j	10	10	0	Y	128	0	63
-def	test	t1	t1	k	k	7	19	0	N	1217	0	63
+def	test	t1	t1	k	k	7	19	0	N	1249	0	63
 def	test	t1	t1	l	l	12	19	0	Y	128	0	63
 def	test	t1	t1	m	m	254	1	0	Y	256	0	8
 def	test	t1	t1	n	n	254	3	0	Y	2048	0	8

mysql-test/r/ps_2myisam.result

@@ -870,7 +870,7 @@ def	test	t_many_col_types	t_many_col_types	c11	c11	0	9	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c12	c12	0	10	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c13	c13	10	10	10	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c14	c14	12	19	19	Y	128	0	63
-def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1217	0	63
+def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1249	0	63
 def	test	t_many_col_types	t_many_col_types	c16	c16	11	8	8	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c17	c17	13	4	4	Y	32864	0	63
 def	test	t_many_col_types	t_many_col_types	c18	c18	1	1	1	Y	32768	0	63

mysql-test/r/ps_3innodb.result

@@ -870,7 +870,7 @@ def	test	t_many_col_types	t_many_col_types	c11	c11	0	9	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c12	c12	0	10	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c13	c13	10	10	10	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c14	c14	12	19	19	Y	128	0	63
-def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1217	0	63
+def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1249	0	63
 def	test	t_many_col_types	t_many_col_types	c16	c16	11	8	8	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c17	c17	13	4	4	Y	32864	0	63
 def	test	t_many_col_types	t_many_col_types	c18	c18	1	1	1	Y	32768	0	63

mysql-test/r/ps_4heap.result

@@ -871,7 +871,7 @@ def	test	t_many_col_types	t_many_col_types	c11	c11	0	9	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c12	c12	0	10	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c13	c13	10	10	10	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c14	c14	12	19	19	Y	128	0	63
-def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1217	0	63
+def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1249	0	63
 def	test	t_many_col_types	t_many_col_types	c16	c16	11	8	8	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c17	c17	13	4	4	Y	32864	0	63
 def	test	t_many_col_types	t_many_col_types	c18	c18	1	1	1	Y	32768	0	63

mysql-test/r/ps_5merge.result

@@ -913,7 +913,7 @@ def	test	t_many_col_types	t_many_col_types	c11	c11	0	9	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c12	c12	0	10	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c13	c13	10	10	10	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c14	c14	12	19	19	Y	128	0	63
-def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1217	0	63
+def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1249	0	63
 def	test	t_many_col_types	t_many_col_types	c16	c16	11	8	8	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c17	c17	13	4	4	Y	32864	0	63
 def	test	t_many_col_types	t_many_col_types	c18	c18	1	1	1	Y	32768	0	63
@@ -2106,7 +2106,7 @@ def	test	t_many_col_types	t_many_col_types	c11	c11	0	9	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c12	c12	0	10	6	Y	32768	4	63
 def	test	t_many_col_types	t_many_col_types	c13	c13	10	10	10	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c14	c14	12	19	19	Y	128	0	63
-def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1217	0	63
+def	test	t_many_col_types	t_many_col_types	c15	c15	7	19	19	N	1249	0	63
 def	test	t_many_col_types	t_many_col_types	c16	c16	11	8	8	Y	128	0	63
 def	test	t_many_col_types	t_many_col_types	c17	c17	13	4	4	Y	32864	0	63
 def	test	t_many_col_types	t_many_col_types	c18	c18	1	1	1	Y	32768	0	63

sql/field.cc

@@ -2877,7 +2877,8 @@ Field_timestamp::Field_timestamp(char *ptr_arg, uint32 len_arg,
   :Field_str(ptr_arg, 19, (uchar*) 0,0,
 	     unireg_check_arg, field_name_arg, table_arg, cs)
 {
-  flags|=ZEROFILL_FLAG; /* 4.0 MYD compatibility */
+  /* For 4.0 MYD and 4.0 InnoDB compatibility */
+  flags|= ZEROFILL_FLAG | UNSIGNED_FLAG;
   if (table && !table->timestamp_field && 
       unireg_check != NONE)
   {