* configure.host (default_newlib_nano_malloc): New.
(msp430): Set it.
* configure.in (newlib_nano_malloc): Leave unset if not set by
the user.
* configure: Regenerate.
* libc/configure.in (NEWLIB_NANO_MALLOC): Set after running
configure.host.
(newlib_nano_malloc): Leave unset if not set by	the user.
* libc/configure: Regenerate.