Update Android port

Update Android port

* build-aux/makecounter.sh (curcount): Rename `counter' to
`emacs_shortlisp_counter'.
* doc/emacs/input.texi (Touchscreens): Document
`touch-screen-extend-selection'.
* doc/lispref/commands.texi (Touchscreen Events): Document
`touchscreen-restart-drag'.
* lisp/touch-screen.el (touch-screen-extend-selection): New user
option.
(touch-screen-restart-drag): New function.
(touch-screen-handle-point-update): Handle `restart-drag'
gestures.
(touch-screen-handle-touch): Check if the prerequisites for
extending a previous drag gesture are met, and generate such
events if so.
(touch-screen-translate-touch): Update doc string.
* src/Makefile.in (otherobj): Remove BUILD_COUNTER_OBJ.
($(lispsource)/international/charprop.el):
(%.elc): Don't depend on bootstrap-emacs if cross configuring
for Android.
(libemacs.so): Directly depend on and link with
BUILD_COUNTER_OBJ.