Prefer 'ARRAYELTS (x)' to 'sizeof x / sizeof *x'

Prefer 'ARRAYELTS (x)' to 'sizeof x / sizeof *x'

* src/comp.c (emit_limple_insn):
* src/msdos.c (dos_set_keyboard, dos_rawgetc):
* src/sysdep.c (convert_speed, list_system_processes):
* src/w32fns.c (deliver_wm_chars, Fx_file_dialog):
* src/w32term.c (record_event, w32_read_socket):
Prefer 'ARRAYELTS (x)' to 'sizeof x / sizeof *x'.

* admin/coccinelle/arrayelts.cocci: New file.

(cherry picked from commit e092aabf714717dd135e5767a49b78c428e49878)