Define JNIEXPORT as visibility default with GCC?

[David DeHaven]

>>> Here's the latest version of the proposed patch:
>>> >
>>> >http://cr.openjdk.java.net/~martin/webrevs/openjdk8/JNIEXPORT/
>>> >
>>> >that has been tested, but only with gcc 4.6,
>>> >but is also written to work with llvm.
>> This looks fine, however since 4.2.1 is still used for some builds we need to filter that specific version out or this will cause grief in other groups.
> I think you meant 4.1.2.

Right, sorry :)

-DrD-