[patch] minor toplevel configure.in simplification

[Doug Evans]

DJ Delorie writes:
 > 
 > > Thus methinks there's no such thing as "always use newlib"
 > 
 > I think the confusion arises because of cygwin - you can't build
 > cygwin's runtime without also building newlib, so it overrides the
 > --with-newlib setting.

Ah. So --with-newlib essentially doesn't exist for this particular target.

Also, clarification.

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.

If 'use installed newlib' were reworded to 'use installed libc'
[which may be newlib but may not be] then I think the suggestion is reasonable.
[fwiw of course]