Fix build problem with Cython v0.24

Fixes #97

capnp/includes/schema_cpp.pxd

@@ -628,6 +628,11 @@ cdef extern from "capnp/schema.capnp.h" namespace " ::capnp::schema":
             void setId(UInt64)
             Value getValue()
             void setValue(Value)
+    cdef cppclass ListNestedNodeReader"capnp::List<capnp::schema::Node::NestedNode>::Reader":
+       ListNestedNodeReader()
+       ListNestedNodeReader(ListNestedNodeReader)
+       Node.NestedNode.Reader operator[](uint)
+       uint size()
 
 cdef extern from "capnp/message.h" namespace " ::capnp":
     cdef cppclass ReaderOptions:

capnp/lib/capnp.pyx

@@ -559,9 +559,9 @@ cdef class _DynamicListBuilder:
         return '<capnp list builder %s>' % <char*>strListBuilder(self.thisptr).cStr()
 
 cdef class _List_NestedNode_Reader:
-    cdef List[C_Node.NestedNode].Reader thisptr
+    cdef C_Node.NestedNode.Reader.ListNestedNodeReader thisptr
     cdef _init(self, List[C_Node.NestedNode].Reader other):
-        self.thisptr = other
+        self.thisptr = <C_Node.NestedNode.Reader.ListNestedNodeReader>other
         return self
 
     def __getitem__(self, index):