Connection.java (getJarFile): download and cache remote jar files.

Connection.java (getJarFile): download and cache remote jar files.

	* gnu/gcj/protocol/jar/Connection.java (getJarFile): download and
	cache remote jar files.
	* gnu/gcj/runtime/VMClassLoader.java: Don't construct jar URL, only
	add File.separator to URL when it is a directory.
	* java/lang/ClassLoader.java: Add Classpath javadoc.
	(parent): final.
	(getParent): Add (disabled) security check.
	(findLibrary): New default method.
	* java/net/JarURLConnection.java (getManifest): Implement.
	(getInputStream): Only create InputStream when entry exists.
	(getHeaders): Only use jarFileURLConnection or JarEntry to set length
	when they exist.
	* java/net/URLClassLoader.java: New/Rewritten version from Classpath.

From-SVN: r59949