nss/nspr: update build/autoconf/config.{guess,sub}

Update the file nss/nspr/build/autoconf/config.guess to the version 2014-03-23.
Update the file nss/nspr/build/autoconf/config.sub to the version 2014-05-01.
Create the file nss/nspr/build/autoconf/GPLv3.txt.

Change-Id: Ifc508a3c1bee57f810588d0013971e4bf1984c10
Reviewed-on: https://gerrit.libreoffice.org/10148
Tested-by: LibreOffice gerrit bot <gerrit@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>