Move bisonexception resolution from flic to slic

The GNU Bison Exception often comes in a different comment and so is detected as an extra license. The GPL bit defines which versions of the GPL it is, whereas the Bison exception bit gives the exception. Therefore, we need code to combine the two appropriately - it can't be done properly with Ignore or Cancel semantics. This code currently lives in flic; it should live in the detector.
