GitHook: make fields outputStream and errorStream private

Subclasses can use the corresponding getter methods.

Change-Id: Iaa9ab01f5a9731a264b28608d2418a9405b601d7
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/hooks/GitHook.java

@@ -44,12 +44,12 @@ abstract class GitHook<T> implements Callable<T> {
 	/**
 	 * The output stream to be used by the hook.
 	 */
-	protected final PrintStream outputStream;
+	private final PrintStream outputStream;
 
 	/**
 	 * The error stream to be used by the hook.
 	 */
-	protected final PrintStream errorStream;
+	private final PrintStream errorStream;
 
 	/**
 	 * Constructor for GitHook.