Update Android port

Update Android port

* java/org/gnu/emacs/EmacsSafThread.java (EmacsSafThread, getCache)
(pruneCache1, pruneCache, cacheChild, cacheDirectoryFromCursor)
(documentIdFromName1, openDocumentDirectory1): Implement the
cache referred to by the commentary.
* java/org/gnu/emacs/EmacsService.java (deleteDocument):
Invalidate the cache upon document removal.
* src/androidvfs.c (android_saf_exception_check)
(android_document_id_from_name): Correctly preserve or set errno
in error cases.