Improve splitting of SQL scripts into statements

[rnorth]

Based on #1563 by @DuanYuePeng, with some minor changes by myself:

Issue 1
for below sql statement, the split function will fail because the table name contains "END".

CREATE TABLE bar (foo VARCHAR(255));
CREATE TABLE gender (gender VARCHAR(255));
CREATE TABLE foo (bar VARCHAR(255));

fixed this issue by checking whether the keywords (END or BEGIN) is separated by any controlling char. eg. '\t', '\n' or ' '.
Issue 2
for below sql statement, the split function will fail because of incorrect inBlockComment flag.

CREATE TABLE bar (foo VARCHAR(255));
/* Insert Values */
INSERT INTO bar (foo) values ('--1');
INSERT INTO bar (foo) values ('--2');

fixed this issue by setting inBlockComment to false after skipping the block comment.

This should fix #1547

[rnorth]

Hmm, both Azure builds are failing on:

GenericContainerRuleTest > sharedMemorySetTest

🤔

[bsideup]

@rnorth it seems to be flaky, I think I've seen this failure on other CIs too...

FYI I just created #1629

[bsideup]

Nice! 👍

[rnorth]

Merging, with what appears to be a flaky test on Travis CI.