fix naming conflict: "__pyx_tuple" is already used as tuple constant prefix

Cython/Compiler/Naming.py

@@ -61,6 +61,7 @@ interned_prefixes = {
     'ustring': pyrex_prefix + "ustring_",
 }
 
+ctuple_type_prefix = pyrex_prefix + "ctuple_"
 args_cname       = pyrex_prefix + "args"
 generator_cname  = pyrex_prefix + "generator"
 sent_value_cname = pyrex_prefix + "sent_value"

Cython/Compiler/PyrexTypes.py

@@ -3643,7 +3643,7 @@ def c_tuple_type(components):
     components = tuple(components)
     tuple_type = c_tuple_types.get(components)
     if tuple_type is None:
-        cname = '__pyx_tuple_' + type_list_identifier(components)
+        cname = Naming.ctuple_type_prefix + type_list_identifier(components)
         tuple_type = c_tuple_types[components] = CTupleType(cname, components)
     return tuple_type