Fix some uses of int instead of EMACS_INT.

Fix some uses of int instead of EMACS_INT.

 minibuf.c (Fminibuffer_contents)
 (Fminibuffer_contents_no_properties)
 (Fminibuffer_completion_contents): Use EMACS_INT for minibuffer
 positions.
 keyboard.c (command_loop_1): Use EMACS_INT to compare point with
 mark.
 alloc.c (make_uninit_string, make_uninit_multibyte_string)
 (allocate_string_data): Accept EMACS_INT for string length.
 editfns.c (Ffield_string, Ffield_string_no_properties)
 (make_buffer_string, make_buffer_string_both, Fbuffer_substring)
 (Fbuffer_substring_no_properties, find_field, Fdelete_field)
 (Ffield_string, Ffield_string_no_properties, Ffield_beginning)
 (Ffield_end): Use EMACS_INT for buffer positions.
 insdel.c (prepare_to_modify_buffer): Use EMACS_INT to compare
 point with mark.
 lisp.h (allocate_string_data, make_uninit_string)
 (make_uninit_multibyte_string, make_buffer_string)
 (make_buffer_string_both): Adjust prototypes.