RFR: Print heap addresses in hs_err

[Roman Kennke]

this change makes ShenandoahHeap::print_on() also print the start and
end of the heap, plus the information from VirtualSpace. I adapted the
latter from VirtualSpace::print_on() instead of calling it because it's
#ifndef PRODUCT. It now prints this info:


Heap
Shenandoah Heap total = 4194304 K, used 212992 K  [0x00000006c0000000,
0x00000007c0000000) Region size = 2048K 
Virtual space:
 - committed: 4294967296
 - reserved:  4294967296
 - [low, high]:     [0x00000006c0000000, 0x00000007c0000000]
 - [low_b, high_b]: [0x00000006c0000000, 0x00000007c0000000]


http://cr.openjdk.java.net/~rkennke/printheapaddrs/webrev.02/

Ok to push?