Utilize more frequently supported file access modes

Utilize more frequently supported file access modes

* java/org/gnu/emacs/EmacsSafThread.java (openDocument1): Use
plain r or w where possible, as the fileio stuff is now better
prepared for FIFOs.
(openDocument): New argument READ.
* java/org/gnu/emacs/EmacsService.java (openDocument): New
argument READ.
* src/android.c (android_init_emacs_service): Adjust
correspondingly.
* src/androidvfs.c (android_saf_file_open): Don't support
O_APPEND.  Pass read as well as trunc and write.