Revert "Avoid some unnecessary traversal in "ForwardDeclareTypes"."

This reverts commit 5204d869.
See https://github.com/cython/cython/issues/3548

Cython/Compiler/ParseTreeTransforms.py

@@ -1510,10 +1510,6 @@ class CnameDirectivesTransform(CythonTransform, SkipDeclarations):
 
 
 class ForwardDeclareTypes(CythonTransform):
-    """
-    Declare all global cdef names that we allow referencing in other places,
-    before declaring everything (else) in source code order.
-    """
 
     def visit_CompilerDirectivesNode(self, node):
         env = self.module_scope
@@ -1557,14 +1553,6 @@ class ForwardDeclareTypes(CythonTransform):
                     entry.type.get_all_specialized_function_types()
         return node
 
-    def visit_FuncDefNode(self, node):
-        # no traversal needed
-        return node
-
-    def visit_PyClassDefNode(self, node):
-        # no traversal needed
-        return node
-
 
 class AnalyseDeclarationsTransform(EnvTransform):