Update Android port

Update Android port

* doc/emacs/android.texi (Android File System): Describe an
easier way to disable scoped storage.
* java/AndroidManifest.xml.in: Add new permission to allow that.
* java/README: Add more text describing Java.
* java/org/gnu/emacs/EmacsContextMenu.java (Item): New fields
`isCheckable' and `isChecked'.
(EmacsContextMenu, addItem): New arguments.
(inflateMenuItems): Set checked status as appropriate.

* java/org/gnu/emacs/EmacsCopyArea.java (perform): Disallow
operations where width and height are less than or equal to
zero.
* lisp/menu-bar.el (menu-bar-edit-menu): Make
execute-extended-command available as a menu item.
* src/androidmenu.c (android_init_emacs_context_menu)
(android_menu_show):
* src/menu.c (have_boxes): Implement menu check boxes.