Old BSD bug: While ^ is recognized and the set of matching characters
is negated, the code neglects to increment the pointer pointing to the
matching characters. Thus, on a negation expression like %[^xyz], the
matching doesn't only stop at x, y, or z, but incorrectly also on ^.
Fix this by setting the start pointer after recognizing the ^.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>