nss: remove undefined behavior and optimize getaddrinfo

nss: remove undefined behavior and optimize getaddrinfo

On x86-64 and compiling with -O2 using stdc_leading_zeros compiles to
the bsr instruction.  The fls function removed by this patch is inlined
but still loops while checking each bit individually.

* nss/getaddrinfo.c: Include <stdbit.h>.
(fls): Remove function.  This function contains a left shift of 31 on an
'int' which is undefined.
(rfc3484_sort): Use stdc_leading_zeros instead of fls.

Signed-off-by: Collin Funk <collin.funk1@gmail.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>