fix: Allow using keywords as alias for columns

[erezrokah]

This fix is similar to #148, to allow using a keyword as a column alias, as SELECT 'Joe' name FROM users is valid (you can check on https://sql.clickhouse.com?query=U0VMRUNUICdKb2UnIG5hbWUgRlJPTSBvdGVsLm90ZWxfbG9ncw)

[coveralls]

Pull Request Test Coverage Report for Build 17836057158

Details

• 6 of 8 (75.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 50.155%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
parser/parser_column.go	6	8	75.0%

Totals
Change from base Build 17815658818:	0.08%
Covered Lines:	7296
Relevant Lines:	14547

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💛 - Coveralls

[git-hulk]

@erezrokah Thanks for your nice catch.