RFR: Implement deoptimization support in Shark

[Roman Kennke]

This change implements support for method deoptimization in Shark, and
thus (re-) enables an optimization for potentially inlining virtual
methods.

http://cr.openjdk.java.net/~rkennke/shark-deopt/webrev.01/

This optimization has been enabled before, a while ago, but has been
disabled because it leads to segmentation faults:

http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=481

I used the testcase in the above bugreport (one of the jtreg tests in
jdk) to verify that the change does indeed deoptimize (and re-compile)
methods correctly. Besides that, no regressions could be found in
hotspot/test/compiler (and a bunch of other tests and programs I've been
running, including SpecJVM, Eclipse, etc).

Ok to go in?

Cheers,
Roman