RFR: JDK-8210705 Stop exporting all symbols on macosx

Mon Sep 24 09:00:41 UTC 2018

For historical reasons, we have exported all symbols on macosx. This was 
an issue that probably arise with the very first macosx port, and the 
complication that we then used map files with a format that Xcode did 
not support.

Now we don't use mapfiles anymore, and there's no reason to keep 
exporting all symbols on macosx. Instead, we should only export the 
public symbols, just like for all other platforms.

All platform-independent code is already properly annotated with 
JNIEXPORT, but there was a few files in libosxapp that needed some 
additional JNIEXPORTs.

Bug: https://bugs.openjdk.java.net/browse/JDK-8210705
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8210705-stop-exporting-all-symbols-on-macosx/webrev.01

/Magnus