fix for queries with both order by and limit

[virattara]

This PR adds support for queries like:
SELECT col_name FROM table_name WHERE id <= 100 ORDER BY date_reg LIMIT 5

[coveralls]

Pull Request Test Coverage Report for Build 58

• 20 of 23 (86.96%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 82.275%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tests/sqlparser_generic.rs	14	15	93.33%
src/sqlparser.rs	6	8	75.0%

Totals
Change from base Build 53:	0.3%
Covered Lines:	2098
Relevant Lines:	2550

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💛 - Coveralls