Bug#118908: make TAGS does not work without having run configure

[Roland McGrath]

> These patches make two changes: the primary makefile will continue
> even if `Makeconf' does not exist; 

Why is this useful?  Makeconf is a source file; it always exists.
 
I made the changes I think you really wanted.  
Now make TAGS works in the source directory.

The .defs support for etags would be nice if you want to do it.
It should be pretty easy with etags --regex.

I have found tags in the generated stubs useful sometimes.
The old code gives you that, if you want to do make TAGS in a build directory.
We could do that in the configured case.  But I don't really care.