Use unlocked stdio more systematically

Use unlocked stdio more systematically

This can improve performance significantly on stdio-bottlenecked code.
E.g., make-docfile is 3x faster on my Fedora 25 x86-64 desktop.
* admin/merge-gnulib (GNULIB_MODULES): Add unlocked-io.
* lib-src/ebrowse.c, lib-src/emacsclient.c, lib-src/etags.c:
* lib-src/hexl.c, lib-src/make-docfile.c, lib-src/movemail.c:
* lib-src/profile.c, lib-src/update-game-score.c:
Include unlocked-io.h instead of stdio.h, since these programs are
single-threaded.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/unlocked-io.h, m4/unlocked-io.m4: New files, copied from Gnulib.
* src/charset.c, src/cm.c, src/emacs.c, src/image.c, src/keyboard.c:
* src/lread.c, src/term.c:
Include sysstdio.h, possibly instead of stdio.h, to define
the unlocked functions if the system does not provide them.
* src/charset.c, src/lread.c (getc_unlocked):
Remove, since sysstdio.h now defines it if needed.
* src/cm.c (cmputc, cmcheckmagic):
* src/dispnew.c (update_frame, update_frame_with_menu)
(update_frame_1, Fsend_string_to_terminal, Fding, bitch_at_user):
* src/emacs.c (main, Fdump_emacs):
* src/fileio.c (Fdo_auto_save, Fset_binary_mode):
* src/image.c (slurp_file, png_read_from_file, png_load_body)
(our_stdio_fill_input_buffer):
* src/keyboard.c (record_char, kbd_buffer_get_event, handle_interrupt):
* src/lread.c (readbyte_from_file):
* src/minibuf.c (read_minibuf_noninteractive):
* src/print.c (printchar_to_stream, strout)
(Fredirect_debugging_output):
* src/sysdep.c (reset_sys_modes, procfs_ttyname)
(procfs_get_total_memory):
* src/term.c (tty_ring_bell, tty_send_additional_strings)
(tty_set_terminal_modes, tty_reset_terminal_modes)
(tty_update_end, tty_clear_end_of_line, tty_write_glyphs)
(tty_write_glyphs_with_face, tty_insert_glyphs)
(tty_menu_activate):
* src/xfaces.c (Fx_load_color_file):
Use unlocked stdio when it should be safe.
* src/sysstdio.h (clearerr_unlocked, feof_unlocked, ferror_unlocked)
(fflush_unlocked, fgets_unlocked, fputc_unlocked, fputs_unlocked)
(fread_unlocked, fwrite_unlocked, getc_unlocked, getchar_unlocked)
(putc_unlocked, putchar_unloced): Provide substitutes if not declared.