RFR (XXS): 8151497: Set REQUIRED_OS_NAME and REQUIRED_OS_VERSION on AIX

[Volker Simonis]

Hi,

can I please have a review and sponsor (because this change requires
the recreation of generated-configure.sh) for this trivial fix:

http://cr.openjdk.java.net/~simonis/webrevs/2016/8151497/
https://bugs.openjdk.java.net/browse/JDK-8151497

For some reason we've never set REQUIRED_OS_NAME and
REQUIRED_OS_VERSION in platform.m4 on AIX. Until now this didn't hurt
but with the upcoming integration of the jigsaw changes from the jake
repository the content of these variables is used during the build for
calling the jmod tool.

Thank you and best regards,
Volker