RFR(XS): 8214063: [AIX] Disable symbol visibility flags

[Volker Simonis]

Hi,

can I please have a review for the following trivial change which
simply disables the symbol visibility flags on AIX:

http://cr.openjdk.java.net/~simonis/webrevs/2018/8214063/
https://bugs.openjdk.java.net/browse/JDK-8214063

Change "8202322: AIX: symbol visibility flags not support on xlc 12.1"
[1] blindly introduced these flags for all xlC compiler versions >
12.1 without ever testing it (which should not have happened). Now
that people are starting to really use xlC 13 it turns out that there
is more to do than just enabling the flags. This future work is
covered by "8204541: Correctly support AIX xlC 13.1 symbol visibility
flags".

Thank you and best regards,
Volker

[1] https://bugs.openjdk.java.net/browse/JDK-8202322
[2] https://bugs.openjdk.java.net/browse/JDK-8204541