Correctly handle non-BMP characters in Android content file names

Correctly handle non-BMP characters in Android content file names

* lisp/term/android-win.el (android-encode-jni)
(android-decode-jni, android-jni): New coding system, for
Android file names and runtime data.

* src/androidterm.h (syms_of_androidvfs): New function.

* src/androidvfs.c (struct android_special_vnode): New field
special_coding_system.
(android_saf_tree_readdir): Decode the file name using the
android-jni coding system.
(special_vnodes): <contents>: Specify a file name coding system.
(android_vfs_convert_name): New function.
(android_root_name): If a special coding system be specified for
a special vnode, convert components to it before invoking its
name function.
(syms_of_androidvfs): New symbol Qandroid_jni.

* src/emacs.c (android_emacs_init): Call syms_of_androidvfs.

(cherry picked from commit e39cb515a108682b520e499c334a600ee634fbf6)