CLEANUP: lists/tree-wide: rename some list operations to avoid some confusion

The current "ADD" vs "ADDQ" is confusing because when thinking in terms
of appending at the end of a list, "ADD" naturally comes to mind, but
here it does the opposite, it inserts. Several times already it's been
incorrectly used where ADDQ was expected, the latest of which was a
fortunate accident explained in 6fa922562 ("CLEANUP: stream: explain
why we queue the stream at the head of the server list").

Let's use more explicit (but slightly longer) names now:

   LIST_ADD        ->       LIST_INSERT
   LIST_ADDQ       ->       LIST_APPEND
   LIST_ADDED      ->       LIST_INLIST
   LIST_DEL        ->       LIST_DELETE

The same is true for MT_LISTs, including their "TRY" variant.
LIST_DEL_INIT keeps its short name to encourage to use it instead of the
lazier LIST_DELETE which is often less safe.

The change is large (~674 non-comment entries) but is mechanical enough
to remain safe. No permutation was performed, so any out-of-tree code
can easily map older names to new ones.

The list doc was updated.
diff --git a/src/mworker-prog.c b/src/mworker-prog.c
index 4113b7c..8d9ce3a 100644
--- a/src/mworker-prog.c
+++ b/src/mworker-prog.c
@@ -70,7 +70,7 @@
 				}
 
 
-				LIST_DEL(&child->list);
+				LIST_DELETE(&child->list);
 				mworker_free_child(child);
 				child = NULL;
 
@@ -183,7 +183,7 @@
 			goto error;
 		}
 
-		LIST_ADDQ(&proc_list, &ext_child->list);
+		LIST_APPEND(&proc_list, &ext_child->list);
 
 	} else if (strcmp(args[0], "command") == 0) {
 		int arg_nb = 0;
@@ -302,7 +302,7 @@
 
 error:
 	if (ext_child) {
-		LIST_DEL(&ext_child->list);
+		LIST_DELETE(&ext_child->list);
 		if (ext_child->command) {
 			int i;