RFR(xs): 8076447: Remove unused MemoryManager::kind()

[Per Liden]

Hi,

Another small cleanup.

MemoryManager and its sub-classes all implement kind(), which is never 
used and can be removed. The enum MemoryManager::Name can then also be 
removed as it's no longer used.

Webrev: http://cr.openjdk.java.net/~pliden/8076447/webrev.0/
Bug: https://bugs.openjdk.java.net/browse/JDK-8076447

/Per