[11] RFR for JDK-8202544: Hide unused exports in libzip

[Alexey Ivanov]

Hi,

Could you please review the following fix for jdk11?

bug: https://bugs.openjdk.java.net/browse/JDK-8202544
webrev: http://cr.openjdk.java.net/~aivanov/8202544/jdk11/webrev.0/

The following exported functions in libzip are not used:
ZIP_GetEntry, ZIP_FreeEntry, ZIP_Lock, ZIP_Unlock, ZIP_Read

I removed JNIEXPORT modifiers from these functions. With the fix, 
they're not exported on Windows; on Linux they're listed as Local rather 
than Global.

I ran tests, no failures.


Thank you in advance.

Regards,
Alexey