RFR: 8232211: Remove dead code from os.hpp|cpp

[Claes Redestad]

Hi,

feel free to review this patch which simply removes a number of
dead and/or effectively unused methods from our os interface

Webrev: http://cr.openjdk.java.net/~redestad/8232211/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8232211

Testing: tier1-2,5 (includes minimal VM builds)

Thanks!

/Claes