This simply makes the code a bit easier to read by giving a name to `match[1]`.

There are a few thing going on in this function which were getting
conflated:

1. Parsing a `directiveType` out of the comment.
2. Ignoring directives that are in line comments but only support block
   comments.
3. Warning on and ignoring line comments that span multiple lines.

Previously these three pieces of functionality were tightly coupled
which made the code harder to read. After this change each task is
handled independently of the other.

Rather than conditionally set a mutable value and check for it at the end of the switch statement, we can actually just handle it inline by using a fallthrough.