Suppress incorrect link warnings for NSS symbols

Suppress incorrect link warnings for NSS symbols

When glibc is built with --enable-static-nss, the warning that
using NSS symbols requires the nss shared objects to be present
is no longer true, as those symbols are built into libc.  Suppress
the warning for those symbols by providing a new macro
(nss_interface_function) for the NSS functions that is defined as
static_link_warning in the normal case, and empty for static NSS.