src/w32*.c: Make functions static.

src/w32*.c: Make functions static.

* src/w32fns.c (w32_wnd_proc, file_dialog_callback):
* src/w32font.c (w32_generic_family):
* src/w32inevt.c (key_event):
* src/w32menu.c (fill_in_menu):
* src/w32proc.c (reader_thread, w32_executable_type, compare_env)
  (merge_and_sort_env, int_from_hex, enum_locale_fn, enum_codepage_fn):
* src/w32term.c (w32_read_socket): Make static.