Bugfixes:
- CVE-2017-5193: Correct a NULL pointer dereference in the nickcmp function
found by Joseph Bisch (GL#1)
- CVE-2017-5194: Correct an error when receiving invalid nick message (GL#4,
#466)
- CVE-2017-5195: Correct an out of bounds read in certain incomplete control
codes found by Joseph Bisch (GL#2)
- CVE-2017-5196: Correct an out of bounds read in certain incomplete
character sequences found by Hanno Böck and independently by J. Bisch
(GL#3)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>