Add support: some mysql sql

[juaby]

Add support:
USE test
SET NAMES UTF8
SELECT @x, @test FROM v.t
SAVEPOINT a6656450_c8fe_4cbc_a75c_37d60d266629
ROLLBACK TO SAVEPOINT 0105c3d0_2750_4d45_be35_f17952cbf389
RELEASE SAVEPOINT 0105c3d0_2750_4d45_be35_f17952cbf389
SET SESSION TRANSACTION MODE
UPDATE LIMIT N|ALL
SELECT LIMIT N, M
Parameter Mark

[coveralls]

Pull Request Test Coverage Report for Build 679561859

• 155 of 169 (91.72%) changed or added relevant lines in 7 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 90.037%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/dialect/mysql.rs	0	2	0.0%
src/ast/mod.rs	24	27	88.89%
src/tokenizer.rs	7	10	70.0%
src/parser.rs	66	72	91.67%

Files with Coverage Reduction	New Missed Lines	%
src/ast/mod.rs	2	72.45%
src/parser.rs	2	86.23%

Totals
Change from base Build 552534083:	0.02%
Covered Lines:	5540
Relevant Lines:	6153

---

💛 - Coveralls

[alamb]

Hi @juaby -- sorry for the delay in review. I am going to help out now with this repo and we are working to clear the backlog. Is this PR still something you would like to work on to help contribute?

[alamb]

I am closing what look like stale PRs in this repo; I apologize in advance if this is a mistake -- please feel free to reopen if you want to keep working on this issue.