RFR(T): 8217716: Remove dead code in PhaseChaitin

[Claes Redestad]

Hi,

various methods and fields in PhaseChaitin and friends are unused and
should be removed.

Bug:    https://bugs.openjdk.java.net/browse/JDK-8217716
Webrev: http://cr.openjdk.java.net/~redestad/8217716/open.00/

At least one of the unused methods (PhaseChaitin::Pre_Simplify)
are linger in product build, so cleaning this up marginally improves
static footprint (-4Kb).

Testing: tier1+2

Thanks!

/Claes