add likely/unlikely to performance critical path

Sinc we are alrady here with likely/unlikely helper, we can make use of it in
our performance critical path. Though the efffect might not be pronounced.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
configure.ac: remove extra trace in PACKAGE_FEATURES

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>