Do not include safe-read.h or full-write; no longer needed.

Do not include safe-read.h or full-write; no longer needed.
(process_signals): Add forward decl.
(SA_NOCLDSTOP, sigprocmask, sigset_t) [!defined SA_NOCLDSTOP]:
New macros.
(siginterrupt) [! HAVE_SIGINTERRUPT]: New macro.
(SA_NODEFER) [!defined SA_NODEFER]: New macro.
(SA_RESETHAND) [!defined SA_RESETHAND]: New macro.
(caught_signals, interrupt_signal, info_signal_count, catch_siginfo):
New vars.
(usage): Mention -USR1 versus -INFO.
(cleanup): Don't invoke print_stats; the caller must do it now.
All callers changed.
(quit): Process signals just before exiting.
(interrupt_handler): Simply record the signal and return.
(siginfo_handler): Simply increment the signal counter and return.
(install_handler): Remove, replacing with:
(install_signal_handlers, process_signals, iread, iwrite):
New functions.  All callers to safe_read and full_write replaced
by iread and iwrite.  All callers to install_handler replaced by
install_handlers.

Do not include inttostr.h, no longer needed.
(print_stats, main): Rewrite and simplify formats to use PRIuMAX
instead of umaxtostr.
(print_stats): Work even in languages that have special
forms for two of things, for r_truncate and w_bytes.  We can't
fix delta_s in this way, since ngettext doesn't support floating-point.
(main): Rewrite to avoid casts.