Install rcs2log within Emacs packages for Android

Install rcs2log within Emacs packages for Android

* doc/emacs/android.texi (Android Environment): Mention the
`rcs2log' program name variable.  Also refine the wording of the
paragraph describing bundled programs a bit.

* doc/lispref/processes.texi (Subprocess Creation): Mention
`rcs2log' and `rcs2log-program-name'.  Correct typos and
spelling mistakes within the variable index.

* etc/NEWS: Amend the announcement of *-program-name to also
cite rcs2log.

* java/Makefile.in (install_temp): Copy rcs2log to
lib/*/librcs2log.so after minor revisions to change the
interpreter name.

* lisp/vc/vc-rcs.el (vc-rcs-rcs2log-program): Ground the program
name upon `rcs2log-program-name'.

* src/callproc.c (syms_of_callproc) <Vrcs2log_program_name>: New
defvar.  Define to `librcs2log.so' under Android, `rcs2log'
elsewhere.