RFR(XS): 8046769: Set T family feature bit on Niagara systems

[Mikael Vidstedt]

Please review this small fix which sets the T family feature bit on 
Niagara systems, which is needed to make an assert in 
src/cpu/sparc/vm/vm_version_sparc.cpp pass (see bug for the assert in 
question).

Bug: https://bugs.openjdk.java.net/browse/JDK-8046769
Webrev: http://cr.openjdk.java.net/~mikael/webrevs/8046769/webrev.00/webrev/

Cheers,
Mikael