Bug fix: Off-by-one error when parsing multiple statements

[fulghum]

An off-by-one error in multistatement parsing prevents us from parsing multistatements without a space between the delimiter and the next statement. For example: "SELECT 1;SELECT 2;" would previously be parsed as "SELECT 1;S" and "ELECT 2;".

Found while testing changes for dolthub/driver#28

[macneale4]

wow. amazing that hasn't come up before. And the test which has the "+1". double wow.

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