Prism: Native libraries on Mac OS X need to have .dylib extension

See RT-19101 for a description of why this is the case.

Currently all native JavaFX libraries loaded via NativeLibLoader have the .jnilib extension. We need to change them all to have the .dylib extension instead.

Affected libraries:

libdecora-sse.jnilib --> libdecora-sse.dylib
libjavafx-font.jnilib --> libjavafx-font.dylib
libjavafx-iio.jnilib --> libjavafx-iio.dylib
libprism-es2.jnilib --> libprism-es2.dylib