Request for reviews (XS): 7048030: is_scavengable changes causing compiler to embed more constants

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7048030/webrev

Fixed 7048030: is_scavengable changes causing compiler to embed more constants

This is the cause of 7047300 problem to appear.  The fix for 7041789 corrected 
the meaning of is_scavengable to really mean what it says.  Unfortunately there 
were some places that were really using it as a proxy for !is_perm.  In 
particular in ciObject::can_be_constant and should_be_constant we will now embed 
constants that we didn't used as long as they are in tenured.  The code should 
be changed from !is_scavengable to is_perm.

Verified with failing test from 7047300.