After JEP 479 is implemented (or more precisely, JDK-8339783 is integrated), we will only define the `JNICALL` define to the empty string on all platforms, since this was only introduced to take care of the special case of 32-bit Windows requiring a `__stdcall` in this location.

While we will need to export the empty definition of JNICALL in jni.h for all eternity to not break user programs, we can remove all other instances of JNICALL in the JDK source base.