Request for reviews (XS): 6951686: Using large pages on Linux prevents zero based compressed oops

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6951686/webrev

Fixed 6951686: Using large pages on Linux prevents zero based compressed oops

The method os::reserve_memory_special() is used with -XX:+UseLargePages on Linux.
It uses shared memory API to reserve memory but it does not use req_addr.

Use req_addr when attaching shared memory segment.