RFR (S) 8080298: Clean up os::...::supports_variable_stack_size()

[Kim Barrett]

On Aug 3, 2015, at 1:51 AM, David Holmes <david.holmes at oracle.com> wrote:
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8080298
> 
> webrev: http://cr.openjdk.java.net/~dholmes/8080298/webrev/
> 
> To support the old LinuxThreads implementation we had to distinguish between threading libraries with fixed-stack-size threads (LinuxThreads), and variable-stack-sized-threads (NPTL). As LinuxThreads support was removed years ago and all the code related to it has now been removed, we have a situation where supports_variable_stack_size() is always true and so the function and its use can be removed.
> 
> While this notion was only ever relevant to Linux it also got copied across to the BSD and AIX ports.

Looks good.