Clean up some redundant or otherwise suspect code

* java/org/gnu/emacs/EmacsOpenActivity.java (onCreate):
Don't check if URI is non-NULL, for instanceof checks this
also.

* java/org/gnu/emacs/EmacsSafThread.java (accessDocument1):
Don't check !writable twice.

* java/org/gnu/emacs/EmacsService.java (documentIdFromName):
Designate this function as public, since it is called
through JNI.

java/org/gnu/emacs/EmacsOpenActivity.java

@@ -533,8 +533,7 @@ public final class EmacsOpenActivity extends Activity
 		else
 		  uri = intent.getParcelableExtra (Intent.EXTRA_STREAM);
 
-		if (uri != null
-		    && (scheme = uri.getScheme ()) != null
+		if ((scheme = uri.getScheme ()) != null
 		    && scheme.equals ("content"))
 		  {
 		    tem1 = EmacsService.buildContentName (uri);