fix AArch64 stack saves and copies

[adinn]

This patch fixes the problem reported here: #236

The patch includes a unit test which manifest the problem and confirms the fix as described in the issyue mentioned above.

[dougxc]

lgtm

[dougxc]

I've started the process for integrating this. I reverted the change in JVMCIVersionCheck as it forces us to prepare a 177 binary internally. The only change really needed is in .travis.yml.

[adinn]

Ok, great. Thanks very much.

[adinn]

I have deleted the unused var stackCopy. I did not detect this error when I ran the eclipseformat command. Is this the right command? Do I need to provide some other arguments to mx?

[dougxc]

This should do it: mx clean; mx build --jdt /path/to/ecj-4.5.1.jar --warning-as-error
You can get ecj-4.5.1.jar here.