Fix mosquitto_evt_tick struct members.

ChangeLog.txt

@@ -1,3 +1,11 @@
+Broker:
+- Fix incorrect datatypes in `struct mosquitto_evt_tick`. This changes the
+  size and offset of two of the members of this struct, and changes the size
+  of the struct. This is an ABI break, but is considered to be acceptable
+  because plugins should never be allocating their own instance of this
+  struct, and currently none of the struct members are used for anything, so a
+  plugin should not be accessing them.
+
 Clients:
 - Fix possible loss of data in `mosquitto_pub -l` when sending multiple long
   lines. Closes #2078.

include/mosquitto_broker.h

@@ -37,6 +37,7 @@ extern "C" {
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <time.h>
 
 struct mosquitto;
 typedef struct mqtt5__property mosquitto_property;
@@ -157,8 +158,8 @@ struct mosquitto_evt_tick {
 	void *future;
 	long now_ns;
 	long next_ns;
-	int now_s;
-	int next_s;
+	time_t now_s;
+	time_t next_s;
 	void *future2[4];
 };