Fix int/EMACS_INT use in process.c and term.c.

Fix int/EMACS_INT use in process.c and term.c.

 term.c (fast_find_position, term_mouse_highlight): Use EMACS_INT
 for buffer positions.
 process.c (read_process_output, send_process)
 (Fprocess_send_region, status_notify): Use EMACS_INT for buffer
 and string positions and size.