Improve appearance of the Android preferences screen

Improve appearance of the Android preferences screen

* .gitignore: Add org/gnu/emacs/R.java.
* cross/Makefile.in (top_builddir): Include verbose.mk.  Rewrite
rules to print nice looking statements.
* doc/emacs/android.texi (Android, Android Startup)
(Android Environment, Android Windowing, Android Fonts):
* doc/emacs/emacs.texi (Top): Add an extra ``Android
Troubleshooting'' node and move troubleshooting details there.
* java/Makefile.in: Generate R.java; improve appearance by using
verbose.mk.

* java/org/gnu/emacs/EmacsPreferencesActivity.java: Reimplement
in terms of PreferencesActivity.
* java/org/gnu/emacs/EmacsView.java (handleDirtyBitmap): Avoid
flicker.
* java/res/xml/preferences.xml: New file.
* src/verbose.mk.in (AM_V_AAPT, AM_V_SILENT): New variables.