libc/glibc: always enable obsolete RPC

Since unrecognised ./configure flags are simply ignored,
we can always pass --enable-obsolete-rpc.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 reporter_name="Harold Grovesteen"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00052.html"

 reporter_comment=""