RFR: 8073545 - Use shorter and more descriptive names for GC worker threads

[David Lindholm]

Hi,

Please review this small fix which changes the names of the GC threads 
to be shorter and more descriptive. There is a limit on 16 characters 
including the terminating null byte for this name, since 
pthread_set_name_np() is used. This change will make it easier to debug, 
as these names shows up in the debugger.

Webrev: http://cr.openjdk.java.net/~brutisso/8073545/webrev.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8073545

Testing: Passed JPRT.


Regards,
David