RFR(XXS): 8067015: Implement os::pd_map_memory() on AIX

[Volker Simonis]

Hi,

could I please get a review for the following trivial change which
simply implements os::pd_map_memory() on AIX:

http://cr.openjdk.java.net/~simonis/webrevs/8067015/

Until now os::pd_map_memory() was only used in the context of class
data sharing (CDS) which isn't supported on AIX anyway, so we hadn't
implemented it in os_aix.cpp

However with the integration of the modularity change,
os::pd_map_memory() is now also needed for the loading of image files.

The implementation is a straightforward copy of the corresponding Linux version.

I'd like to push this directly to jdk9/dev/hotspot because it was
introduced there and because it affects all our AIX builds. I hope
that's no problem, especially because the change only touches an
AIX-only files.

Thank you and best regards,
Volker