patch 7.4.2101

Problem:    Looping over windows, buffers and tab pages is inconsistant.
Solution:   Use FOR_ALL_ macros everywhere. (Yegappan Lakshmanan)

src/edit.c

@@ -4239,7 +4239,7 @@ ins_compl_get_exp(pos_T *ini)
 
     if (!compl_started)
     {
-	for (ins_buf = firstbuf; ins_buf != NULL; ins_buf = ins_buf->b_next)
+	FOR_ALL_BUFFERS(ins_buf)
 	    ins_buf->b_scanned = 0;
 	found_all = FALSE;
 	ins_buf = curbuf;