libc/newlib: update fetch location

The menu system provides an option to allow a user to request newlib
version 2.0.0. newlib-2.0.0, however, is not available at the download
location currently being used. It is, however, available (as are other
supported versions of newlib) at an alternate location.

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Message-Id: <75ab5151c7f5dc9086e3.1362334313@suse64>
Patchwork-Id: 224561

 reporter_name="Yann E. MORIN"

 reporter_url="http://ymorin.is-a-geek.org/"

 reporter_comment="Toolchain for the Raspberry Pi, with hard-float."