Support SQLite CREATE VIRTUAL TABLE

[miuy56dc]

Support SQLite CREATE VIRTUAL TABLE

[coveralls]

Pull Request Test Coverage Report for Build 150138763

• 37 of 44 (84.09%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 91.781%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser.rs	13	15	86.67%
src/ast/mod.rs	10	15	66.67%

Files with Coverage Reduction	New Missed Lines	%
src/ast/mod.rs	1	80.76%

Totals
Change from base Build 148650756:	-0.03%
Covered Lines:	4221
Relevant Lines:	4599

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💛 - Coveralls

[nickolay]

I think that we'll eventually fold the CreateVirtualTable AST variant into the generic Statement::CreateTable (and re-use the table schema parser for module_args), but I think this is good for now. Thanks!

Please note that it's preferable to use one of the verified_... methods in the test, instead of duplicating the SQL text in the tests (60f60d9)