package/asterisk: security bump to version 16.4.1

package/asterisk: security bump to version 16.4.1

Fixes the following security issues:

CVE-2019-12827: A specially crafted SIP in-dialog MESSAGE message can cause
Asterisk to crash:

https://downloads.asterisk.org/pub/security/AST-2019-002.html

CVE-2019-13161: When T.38 faxing is done in Asterisk a T.38 reinvite may be
sent to an endpoint to switch it to T.38.  If the endpoint responds with an
improperly formatted SDP answer including both a T.38 UDPTL stream and an
audio or video stream containing only codecs not allowed on the SIP peer or
user a crash will occur.  The code incorrectly assumes that there will be at
least one common codec when T.38 is also in the SDP answer:

https://downloads.asterisk.org/pub/security/AST-2019-003.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>