package/mosquitto: bump to version 1.6.4

Bugfix release, fixing a number of issues.  For details, see the
announcement:

https://mosquitto.org/blog/2019/08/version-1-6-4-released/

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

package/mosquitto/mosquitto.hash

@@ -1,5 +1,5 @@
 # Locally calculated after checking gpg signature
-sha256 9ef5cc75f4fe31d7bf50654ddf4728ad9e1ae2e5609a4b42ecbbcb4a209ed17e  mosquitto-1.6.3.tar.gz
+sha256 a3d5822c249f6a6e13311b1b09eff6807ea01608a5a77934e1769842e9d146ef  mosquitto-1.6.4.tar.gz
 
 # License files
 sha256 cc77e25bafd40637b7084f04086d606f0a200051b61806f97c93405926670bc1  LICENSE.txt

package/mosquitto/mosquitto.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-MOSQUITTO_VERSION = 1.6.3
+MOSQUITTO_VERSION = 1.6.4
 MOSQUITTO_SITE = https://mosquitto.org/files/source
 MOSQUITTO_LICENSE = EPL-1.0 or EDLv1.0
 MOSQUITTO_LICENSE_FILES = LICENSE.txt epl-v10 edl-v10