hsail support for different compression for klass ptrs vs. oops

[Deneau, Tom]

All --

I have posted a small webrev for hsail support for different compression for klass ptrs vs. oops to 
http://cr.openjdk.java.net/~tdeneau/graal-webrevs/webrev-compressed-klass-ptrs/webrev/ 

We had an java8 based instanceof based test that started failing when graal started supporting different compressions for klass ptrs vs. oops.  I have added a java7 version of this test.

Brief Summary:
  * HSAILHotSpotLIRGenerator passes possibly different base and shift for oops and klass ptrs to the lower layers.
  * Avoids the overhead of testing for null on klass ptrs.

Could you please look this over?

-- Tom