RFR(s): 8076294: Cleanup of CollectedHeap::kind()

[Per Liden]

Hi,

Another small cleanup.

CollectedHeap::kind() currently returns CollectedHeap::Abstract, which 
makes little sense. Changing it to be a pure virtual member function 
instead. The Abstract and SharedHeap members of CollectedHeap::Name can 
then be removed as they are never used.

Webrev: http://cr.openjdk.java.net/~pliden/8076294/webrev.0/

Bug: https://bugs.openjdk.java.net/browse/JDK-8076294

Testing: jprt

cheers,
/Per