Use a free-list for dbChannel and chFilter objects.

Have to make sure the dbChannel subsystem is initialized
properly when testing though.

src/std/filters/test/dbndTest.c

@@ -116,6 +116,7 @@ MAIN(dbndTest)
 
     testPlan(59);
 
+    dbChannelInit();
     evtctx = db_init_events();
 
     if (dbReadDatabase(&pdbbase, "dbndTest.dbd",

src/std/filters/test/syncTest.c

@@ -143,6 +143,7 @@ MAIN(syncTest)
 
     testPlan(0);
 
+    dbChannelInit();
     evtctx = db_init_events();
 
     if (dbReadDatabase(&pdbbase, "syncTest.dbd",

src/std/filters/test/tsTest.c

@@ -57,6 +57,7 @@ MAIN(tsTest)
 
     testPlan(12);
 
+    dbChannelInit();
     evtctx = db_init_events();
 
     if (dbReadDatabase(&pdbbase, "tsTest.dbd",