2685_warn_undeclared: fix undeclared type warnings for unpickle variables.

The types of variables __pyx_PickleError, __pyx_result from generated
unpickle function, and variables state, _dict from __reduce_cython__
generated method were not declared.
So warnings were raised with warn.undeclared for every single extension
type.

Now, we define the type of these variables, and no warnings are raised.

Cython/Compiler/ParseTreeTransforms.py

@@ -1707,6 +1707,8 @@ if VALUE is not None:
             # so it can be pickled *after* self is memoized.
             unpickle_func = TreeFragment(u"""
                 def %(unpickle_func_name)s(__pyx_type, long __pyx_checksum, __pyx_state):
+                    cdef object __pyx_PickleError
+                    cdef object __pyx_result
                     if __pyx_checksum != %(checksum)s:
                         from pickle import PickleError as __pyx_PickleError
                         raise __pyx_PickleError("Incompatible checksums (%%s vs %(checksum)s = (%(members)s))" %% __pyx_checksum)
@@ -1735,6 +1737,8 @@ if VALUE is not None:
 
             pickle_func = TreeFragment(u"""
                 def __reduce_cython__(self):
+                    cdef tuple state
+                    cdef object _dict
                     cdef bint use_setstate
                     state = (%(members)s)
                     _dict = getattr(self, '__dict__', None)