lexer: handle multiline comment after keyword

[blotus]

Hello,

While testing your (excellent) library, we found a corner case in which SQL keywords were not properly detected when followed directly by a multiline comment.

Before this change, the query select/**/*/**/from/**/events would get tokenized as:

select/
*
*
/*/**/
from/
*
*
/
events

Note the / from the comment being part of select.

With this change, it now gets parsed as:

select
/**/
*
/**/
from
/**/
events