influxql: $ character sometimes accepted as whitespace

[mark-rushakoff]

Working from 921e4f5. There appear to be several cases where $ is accepted in a query, when it looks like it should be invalid:

> $show$databases
name: databases
---------------
name
_internal
z

> $show$measurements
name: measurements
------------------
name
m
t

> select*$from m
name: m
-------
time            i
1468529979248078256 0

[jsternberg]

@jwilder do you think we can get this into 1.0?

[jsternberg]

This is not going to end up in 1.0. I'm setting the milestone for 1.1 and putting up a PR to get it into master.

@rkuchan until this is merged, there's going to be an issue with bound parameters. If you use a keyword like $SHOW, the scanner ignores the dollar sign and treats it as SHOW. This applies to any keyword. Everything else should be fine.