mosquitto: update to 1.5.7

This is a minor bugfix release. Full changelog available at:
https://mosquitto.org/blog/2019/02/version-1-5-7-released/

Most relevant to OpenWrt are probably:
* fixing persistent store bloat
* fix sorting of included config files
* fix errors related to per_listener_settings

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

net/mosquitto/Makefile

@@ -9,7 +9,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mosquitto
-PKG_VERSION:=1.5.6
+PKG_VERSION:=1.5.7
 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:=d5bdc13cc668350026376d57fc14de10aaee029f6840707677637d15e0751a40
+PKG_HASH:=d4024c3388502d50be4192991e90d66dfb344376104df3f63846c9f201779955
 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(BUILD_VARIANT)/$(PKG_NAME)-$(PKG_VERSION)
 
 include $(INCLUDE_DIR)/package.mk