[MEDIUM] Fix memory freeing at exit

New functions implemented:
 - deinit_pollers: called at the end of deinit())
 - prune_acl: called via list_for_each_entry_safe

Add missing pool_destroy2 calls:
 - p->hdr_idx_pool
 - pool2_tree64

Implement all task stopping:
 - health-check: needs new "struct task" in the struct server
 - queue processing: queue_mgt
 - appsess_refresh: appsession_refresh

before (idle system):
==6079== LEAK SUMMARY:
==6079==    definitely lost: 1,112 bytes in 75 blocks.
==6079==    indirectly lost: 53,356 bytes in 2,090 blocks.
==6079==      possibly lost: 52 bytes in 1 blocks.
==6079==    still reachable: 150,996 bytes in 504 blocks.
==6079==         suppressed: 0 bytes in 0 blocks.

after (idle system):
==6945== LEAK SUMMARY:
==6945==    definitely lost: 7,644 bytes in 137 blocks.
==6945==    indirectly lost: 9,913 bytes in 587 blocks.
==6945==      possibly lost: 0 bytes in 0 blocks.
==6945==    still reachable: 0 bytes in 0 blocks.
==6945==         suppressed: 0 bytes in 0 blocks.

before (running system for ~2m):
==9343== LEAK SUMMARY:
==9343==    definitely lost: 1,112 bytes in 75 blocks.
==9343==    indirectly lost: 54,199 bytes in 2,122 blocks.
==9343==      possibly lost: 52 bytes in 1 blocks.
==9343==    still reachable: 151,128 bytes in 509 blocks.
==9343==         suppressed: 0 bytes in 0 blocks.

after (running system for ~2m):
==11616== LEAK SUMMARY:
==11616==    definitely lost: 7,644 bytes in 137 blocks.
==11616==    indirectly lost: 9,981 bytes in 591 blocks.
==11616==      possibly lost: 0 bytes in 0 blocks.
==11616==    still reachable: 4 bytes in 1 blocks.
==11616==         suppressed: 0 bytes in 0 blocks.

Still not perfect but significant improvement.
diff --git a/src/fd.c b/src/fd.c
index 9c370fa..eaaaabf 100644
--- a/src/fd.c
+++ b/src/fd.c
@@ -87,6 +87,22 @@
 }
 
 /*
+ * Deinitialize the pollers.
+ */
+void deinit_pollers() {
+
+	struct poller *bp;
+	int p;
+
+	for (p = 0; p < nbpollers; p++) {
+		bp = &pollers[p];
+
+		if (bp && bp->pref)
+			bp->term(bp);
+	}
+}
+
+/*
  * Lists the known pollers on <out>.
  * Should be performed only before initialization.
  */