RFR [9] 8139706: JarFile.getBytes could use InputStream.readNBytes

[Claes Redestad]

Hi all,

java.util.jar.JarFile could be improved further by using 
InputStream.readNBytes when there's information in the ZipEntry about 
the entry size.

Webrev: http://cr.openjdk.java.net/~redestad/8139706/webrev.01/
Bug: https://bugs.openjdk.java.net/browse/JDK-8139706

Testing: verified improvements in internal startup/footprint tests

/Claes