review(XXS): 7060842: UseNUMA crash with UseHugreTLBFS running SPECjvm2008

[Igor Veresov]

It seems that madvise(MADV_FREE) breaks pages reservation semantics of 
the the underlying segment. With tight memory constraints this would 
cause a race for pages and a segfault if the JVM louses. The solution is 
to revert back to the previous implementation of os::free_memory() that 
used mmap().

Webrev: http://cr.openjdk.java.net/~iveresov/7060842/webrev.00/

Tested is gc test suite.

igor