mpi/longlong: make use of compiler provided builtin_ctz/builtin_clz
* configure.ac (gcry_cv_have_builtin_ctzl, gcry_cv_have_builtin_clz) (gcry_cv_have_builtin_clzl): New checks. * mpi/longlong.h (count_leading_zeros, count_trailing_zeros): Use __buildin_clz[l]/__builtin_ctz[l] if available and bit counting macros not yet provided by inline assembly.
- Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>