pjsip: Add timer refactor patch and timer 0 cancellation.

There have been numerous timer issues over the years which
resulted in Teluu doing a major refactor of the timer
implementation whereby the timer entries themselves are not
trusted. This change backports this refactor which has
been shown to resolve timer crashes.

Additionally another patch has been backported to prevent
timer entries with an internal id of 0 from being canceled.
This would result in the invalid timer id of 0 being placed
into the timer heap causing issues. This is also a backport.

Change-Id: I1ba318b1f153a6dd7458846396e2867282b428e7
(cherry picked from commit 9ce6d46aea)

third-party/pjproject/patches/0041-pjlib_cancel_timer_0.patch

@@ -0,0 +1,39 @@
+commit 40dd48d10911f4ff9b8dfbf16428fbc9acc434ba
+Author: Riza Sulistyo <trengginas@users.noreply.github.com>
+Date:   Thu Jul 9 17:47:24 2020 +0700
+
+    Modify timer_id check on cancel() (#2463)
+    
+    * modify timer_id check on cancel().
+    
+    * modification based on comments.
+
+diff --git a/pjlib/include/pj/timer.h b/pjlib/include/pj/timer.h
+index b738a6e76..4b76ab65d 100644
+--- a/pjlib/include/pj/timer.h
++++ b/pjlib/include/pj/timer.h
+@@ -120,7 +120,10 @@ typedef struct pj_timer_entry
+ 
+     /** 
+      * Internal unique timer ID, which is assigned by the timer heap. 
+-     * Application should not touch this ID.
++     * Positive values indicate that the timer entry is running, 
++     * while -1 means that it's not. Any other value may indicate that it 
++     * hasn't been properly initialised or is in a bad state.
++     * Application should not touch this ID. 
+      */
+     pj_timer_id_t _timer_id;
+ 
+diff --git a/pjlib/src/pj/timer.c b/pjlib/src/pj/timer.c
+index 66516fce8..34966c481 100644
+--- a/pjlib/src/pj/timer.c
++++ b/pjlib/src/pj/timer.c
+@@ -535,7 +535,7 @@ static int cancel( pj_timer_heap_t *ht,
+     PJ_CHECK_STACK();
+ 
+     // Check to see if the timer_id is out of range
+-    if (entry->_timer_id < 0 || (pj_size_t)entry->_timer_id > ht->max_size) {
++    if (entry->_timer_id < 1 || (pj_size_t)entry->_timer_id >= ht->max_size) {
+ 	entry->_timer_id = -1;
+     	return 0;
+     }