util:check character set capitalization when creating a table

[ciscoxll]

What have you changed? (mandatory)

This pr fix problem check character set capitalization when creating a table.

MySQL [ltest]> create table t5(id int) charset=UTF8;
ERROR 1115 (42000): Unknown character set: 'UTF8'

MySQL [ltest]> create table t5(id int) charset=utf8;
Query OK, 0 rows affected (0.13 sec)

What are the type of the changes (mandatory)?

Bug fix.

How has this PR been tested (mandatory)?

Unit tests.

[ciscoxll]

@zimulala @winkyao @shenli PTAL.

[jackysp]

Should the title be creating a table?

[zimulala]

LGTM

[ciscoxll]

/run-all-tests

[crazycs520]

LGTM

[jackysp]

LGTM