RFR: 8251365: Build failure on AIX after 8250636

[Dmitry Cherepanov]

Please review the fix for build failure on AIX. With this change, "tm_gmtoff" is used only if _ALLBSD_SOURCE or _GNU_SOURCE is set. In the case of AIX, we'll continue to use "timezone".

I'll start jdk-submit testing for this change shortly, unfortunately I do not have an AIX machine at hand and would appreciate if someone (with access to AIX) could verify that the change fixes AIX build . Thanks in advance.

JBS: https://bugs.openjdk.java.net/browse/JDK-8251365
Webrev: http://cr.openjdk.java.net/~dcherepanov/8251365/webrev.v1/

Thanks,

Dmitry