[libava/win32]: Don't add dll[im/ex]port attributes to libgcj, unless dll build

[Tom Tromey]

>>>>> "Bryce" == Bryce McKinlay <bryce@mckinlay.net.nz> writes:

Bryce> Right. Sounds good to me - go ahead and write up a patch to get
Bryce> rid of GCJ_JNI_IMPL etc, and I'll approve it if nobody else
Bryce> objects ;-)

I think we still need __GCJ_JNI_IMPL__ in a few places.  Getting rid
of the JNIIMPEXP macro and that use of __GCJ_JNI_IMPL__ is fine by me
though.

Tom