Request for reviews (XS): 7106944: assert(_pc == *pc_addr) failed may be too strong

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/7106944/

7106944: assert(_pc == *pc_addr) failed may be too strong
Reviewed-by:

Sometimes we are already deoptimizing a frame when we request another
deoptimization of the same frame.  This makes the assert to fail.

The fix is to add a check to the assert that the return address is the
same that we are going to patch.

src/cpu/x86/vm/frame_x86.cpp