Implement art_quick_string_compareto entrypoint for x86-64

This adds implementation of the art_quick_string_compareto
entrypoint for the x86-64 platform.

Add a test to stub_test, enabled for arm, x86 and x86-64.

Change-Id: I71b318b03d4c8920ccb3723b59c43542e219bf47
Signed-off-by: Alexei Zavjalov <alexei.zavjalov@intel.com>
2 files changed