Support CREATE TABLE x AS TABLE y

[sarahyurick]

Closes #614

My solution was to parse CREATE TABLE x AS TABLE y the same as CREATE TABLE x AS SELECT * FROM y.

[coveralls]

Pull Request Test Coverage Report for Build 3587526224

• 62 of 72 (86.11%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.001%) to 86.345%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ast/query.rs	7	10	70.0%
src/parser.rs	26	33	78.79%

Files with Coverage Reduction	New Missed Lines	%
src/ast/query.rs	1	84.77%

Totals
Change from base Build 3586103034:	-0.001%
Covered Lines:	12242
Relevant Lines:	14178

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💛 - Coveralls

[sarahyurick]

Hi @alamb, let me know if these updates look reasonable 🙂

[alamb]

Sorry for the delay in review @sarahyurick -- this is looking better but not quite ready yet I think

[alamb]

👍

[sarahyurick]

Thanks @alamb ! Updated to use peek_token() (and also peek_nth_token()) and does not fail on your whitespace example anymore. I wasn't exactly sure how to use parse_identifier() for this, but hopefully the logic for parse_as_table() should be a lot cleaner now.

[alamb]

Thanks @sarahyurick -- I think this PR now looks good. I have some ideas of how to simplify the code a little more but I'll make a follow on PR with that change.

Thanks again for sticking with this