Update Android port

Update Android port

* doc/emacs/android.texi (Android Document Providers): Improve
wording of paragraph clarifying limits on subprocesses.
* java/org/gnu/emacs/EmacsService.java (getDocumentTrees): Use
Java standard US-ASCII coding standard instead of the
undocumented ``ASCII'' alias.
(decodeFileName): Remove unused function.
(documentIdFromName):
* src/android.c (android_init_emacs_service): Take a String for
NAME instead of a byte array.
* src/androidvfs.c (android_verify_jni_string): New function.
(android_document_id_from_name): Verify that STRING is a valid
Modified UTF-8 string.