RFR(S) 8038399: Remove dead oop_iterate MemRegion variants from SharedHeap, Generation and Space classes

[Mikael Gerdin]

Hi,

I'm doing some cleanups in the "Space" classes to simplify the code for the G1 
class unloading work[1].
Here's a simple dead code deletion change (except for in generation.cpp):

Bug: https://bugs.openjdk.java.net/browse/JDK-8038399
Webrev: http://cr.openjdk.java.net/~mgerdin/8038399/webrev.0

/Mikael

[1] http://openjdk.java.net/jeps/156