Update Android port

Update Android port

* src/androidterm.c (NATIVE_NAME, JNICALL)
(android_build_extracted_text, android_update_selection): Use
0-based indices for Android buffer positions.  Also, report
surrounding text relative to the region, not to the cursor.
* src/textconv.c (textconv_query): Accept new values of
position.
(really_set_composing_text): Use ephemeral last point.