Adding x86 compiler utils instructions and tests

Instructions added are (repne scasb), (repne movb),
and (repne cmpsb) for x86.
Instructions added is (repne scasb) for x86_64.

Test: m -j31 test-art-host-gtest-assembler_x86_test
      m -j31 test-art-host-gtest-assembler_x86_64_test

Change-Id: I137bf5fe1174b1dcc0166f7f2e0cffadbc0ca7f5
6 files changed