Use shortcuts for Flength

Use shortcuts for Flength

When calculating the length of a Lisp object whose type is
known, use a specialized length operation on it to save a bit
of runtime overhead.
* src/callint.c (Fcall_interactively):
* src/minibuf.c (read_minibuf_unwind):
Use ASIZE rather than Flength on values that must be vectors.
* src/charset.c (Fsort_charsets):
* src/coding.c (detect_coding_sjis):
(Fdefine_coding_system_internal):
* src/data.c (wrong_choice):
* src/eval.c (Flet, eval_sub, Fapply, apply_lambda):
* src/fns.c (sort_list):
* src/font.c (font_vconcat_entity_vectors)
(font_find_for_lface):
* src/frame.c (Fmodify_frame_parameters):
* src/fringe.c (get_logical_fringe_bitmap):
* src/ftfont.c (ftfont_get_open_type_spec):
* src/gtkutil.c (xg_print_frames_dialog):
* src/lread.c (read1, read_vector):
* src/keymap.c (Fkey_description):
* src/kqueue.c (Fkqueue_add_watch):
* src/macfont.m (macfont_get_open_type_spec):
* src/menu.c (parse_single_submenu, x_popup_menu_1):
* src/minibuf.c (Finternal_complete_buffer):
* src/nsfont.m (ns_findfonts, nsfont_list_family):
* src/process.c (Fmake_process):
* src/search.c (Fset_match_data):
* src/xfaces.c (Fx_family_fonts):
Use list_length rather than Flength on values that must be lists.
* src/fns.c (list_length): New function.
(Flength): Use it.
* src/nsfont.m (ns_findfonts):
Use !NILP (x) rather than XFIXNUM (Flength (x)) != 0.
* src/xdisp.c (store_mode_line_string):
Use SCHARS rather than Flength on values that must be strings.