parser: change intLit to decLit when the value out of range

[tiancaiamao]

If lexer get a intLit and it's out of uint64 range, change it to decimal.
This PR will fix #2946

mysql> create table test (id decimal(30, 0));
Query OK, 0 rows affected (0.00 sec)

mysql>  insert into test values(123456789012345678901234567890);
ERROR 1105 (HY000): line 0 column 54 near ")"integer literal: strconv.ParseUint: parsing "123456789012345678901234567890": value out of range (total length 55)

[tiancaiamao]

@coocood @shenli

[shenli]

LGTM
@coocood @zimulala PTAL

[zimulala]

mysql> select 123456789012345678903245352784573928475684357639284579432758493574389568374312985695643856743825647835643728;
+--------------------------------------------------------------------------------------------------------------+
| 123456789012345678903245352784573928475684357639284579432758493574389568374312985695643856743825647835643728 |
+--------------------------------------------------------------------------------------------------------------+
|                                            99999999999999999999999999999999999999999999999999999999999999999 |
+--------------------------------------------------------------------------------------------------------------+

[zimulala]

LGTM

[coocood]

LGTM