[patch] minor toplevel configure.in simplification

[Doug Evans]

Nathanael Nerode writes:
 > I want to do more cleanup on the stuff related to deciding what to do with
 > newlib, but I have to figure out what the correct behavior of '--without-newlib'
 > on 'always use newlib' targets is.  I'm thinking it should mean 'use installed
 > newlib, not the one in the tree', but I'd love it if someone else could 
 > confirm that that's reasonable behavior.

I wonder if it depends on one's meaning of "always".
Is it a misnomer?

There should be no reason a user of any port can't supply their
own libc/libm/blah.

Thus methinks there's no such thing as "always use newlib"
[instead it should be "default to newlib"]
and --without-newlib means what it says it means: don't use newlib,
not even an installed one.