fix building the core with --disable-unicode

I changed some bytearray methods to use strings instead of unicode like bytes_repr
Also, bytearray.fromhex() can take strings as well as unicode
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 9b47819..4d71591 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -784,7 +784,9 @@
 	(void)PyFrame_ClearFreeList();
 	(void)PyCFunction_ClearFreeList();
 	(void)PyTuple_ClearFreeList();
+#ifdef Py_USING_UNICODE
 	(void)PyUnicode_ClearFreeList();
+#endif
 	(void)PyInt_ClearFreeList();
 	(void)PyFloat_ClearFreeList();
 }