util: add ly_list_iter

Add a new function to go through a libyang list, equivalent to
LY_LIST_FOR.

Closes: #102
Signed-off-by: Stefan Gula <steweg@gmail.com>
Signed-off-by: Samuel Gauthier <samuel.gauthier@6wind.com>

Author: samuel-gauthier

libyang/util.py

@@ -59,6 +59,14 @@ def ly_array_iter(cdata):
         yield cdata[i]
 
 
+# -------------------------------------------------------------------------------------
+def ly_list_iter(cdata):
+    item = cdata
+    while item != ffi.NULL:
+        yield item
+        item = item.next
+
+
 # -------------------------------------------------------------------------------------
 class IOType(enum.Enum):
     FD = enum.auto()