Fix Bug 843: Remove  Platform's requirement and use of TempJarCache.bootstrapNativeLib(),  allowing versatile use of 1st native jar file (big-java-jar w/  big-native-jar)

The remaining Platform dependency existed in IOUtil.copyStream2Stream(..), used by JarUtil.extract(..),
i.e. the MachineDescription's PAGE_SIZE.

Solved by using a const buffer size of 4096 bytes.