Fix int/EMACS_INT use in lread.c, marker.c, minibuf.c, print.c

Fix int/EMACS_INT use in lread.c, marker.c, minibuf.c, print.c

 print.c (print_object, print_string, strout): Use EMACS_INT for
 string indices.
 minibuf.c (string_to_object): Use EMACS_INT for string position
 and size.
 marker.c (verify_bytepos): Use EMACS_INT for buffer positions.
 lread.c <read_from_string_index, read_from_string_index_byte>
 <read_from_string_limit, readchar_count>: Define EMACS_INT.
 (readchar, unreadchar, read_internal_start): Use EMACS_INT for
 buffer positions and string length.