Implementation of integer intrinsics on x86_64

Rationale:
Efficient implementations of common integer operations.
Already tested in:
  564-checker-bitcount
  565-checker-rotate:
  566-checker-signum
  567-checker-compare
  568-checker-onebit  (extended to deal with run-time zero)

Change-Id: Ib48c76eee751e7925056d7f26797e9a9b5ae60dd