net/mosquitto: Update to 1.6.12

Security release.  From the changelog:

- In some circumstances, Mosquitto could leak memory when handling PUBLISH
  messages. This is limited to incoming QoS 2 messages, and is related
  to the combination of the broker having persistence enabled, a clean
  session=false client, which was connected prior to the broker restarting,
  then has reconnected and has now sent messages at a sufficiently high rate
  that the incoming queue at the broker has filled up and hence messages are
  being dropped. This is more likely to have an effect where
  max_queued_messages is a small value. This has now been fixed. Closes
  https://github.com/eclipse/mosquitto/issues/1793

Changelog: https://mosquitto.org/blog/2020/08/version-1-6-12-released/

Signed-off-by: Karl Palsson <karlp@etactica.com>

net/mosquitto/Makefile

@@ -9,7 +9,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mosquitto
-PKG_VERSION:=1.6.11
+PKG_VERSION:=1.6.12
 PKG_RELEASE:=1
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE.txt
@@ -17,7 +17,7 @@ PKG_CPE_ID:=cpe:/a:eclipse:mosquitto
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://mosquitto.org/files/source/
-PKG_HASH:=b02d8f1368c40d5779ee125c37daf9003608eb47d7fbb04c5b938c76c1230a1f
+PKG_HASH:=548d73d19fb787dd0530334e398fd256ef3a581181678488a741a995c4f007fb
 
 include $(INCLUDE_DIR)/package.mk