[PATCH 1/3] integer/clz: Use clang builtin instead of llvm asm

The generated llvm IR mostly identical. char/uchar case is a bit worse.

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>