Update Android port

Update Android port

* java/org/gnu/emacs/EmacsContextMenu.java (display): Use
`EmacsHolder' instead of `Holder'.
* java/org/gnu/emacs/EmacsDialog.java (toAlertDialog): Use
`EmacsDialogButtonLayout' to ensure that buttons are wrapped
properly.
(display): Adjust for new holder class.
* java/org/gnu/emacs/EmacsDialogButtonLayout.java
(EmacsDialogButtonLayout, onMeasure, onLayout): New functions.

* java/org/gnu/emacs/EmacsDrawLine.java:
* java/org/gnu/emacs/EmacsFillPolygon.java: Remove redundant
imports.
* java/org/gnu/emacs/EmacsHolder.java (EmacsHolder<T>):
* java/org/gnu/emacs/EmacsService.java (class Holder<T>)
(getEmacsView, EmacsService): Rename `Holder' to `EmacsHolder'
and make it public.