wrong unit for TIMEFMT=%M

[Stephane Chazelas <stephane@chazelas.org>]

TIMEFMT=%M is meant to report memory usage in KiB, but it's not the
case in Linux and FreeBSD at least.

It seems like zsh's TIMEFMT has had a tormented history.

For %M,

2.00.03 had

case 'M': fprintf(stderr,"%ld",ru->ru_maxrss); break

In 2.2, that changed to

#if sun
case 'M': fprintf(stderr,"%ld",ru->ru_maxrss*pk); break;
#else
fprintf(stderr, "%ld", ru->ru_maxrss / 1024);
#endif

(pk being the number of KiB per page).

It seemed to disappear altogether in 2.6 and came back circa
4.0.4 as 

fprintf(stderr, "%ld", ru->ru_maxrss / 1024);

GNU time's configure.ac has:

# What memory units are reported by getrusage(2) ?
warn_getrusage_mem_units=
if test -z "$time_getrusage_mem_units" ; then
  # if envvar 'time_getrusage_mem_units' isn't set,
  # autodetect based on OS.
  case "$host_os" in
    minix*|aix*|*bsd*|linux*|gnu*)
                     time_getrusage_mem_units=kb ;;

    macos*|darwin*)  time_getrusage_mem_units=bytes ;;

    solaris*)        time_getrusage_mem_units=pages ;;

    # As a fallback, assume KB (the most common value).
    # Set the 'warn' variable to warn the user at the end
    # of ./configure
    *) time_getrusage_mem_units=kb
       warn_getrusage_mem_units=yes
       ;;
  esac
fi

Suggesting zsh is only correct on macos/darwin atm.

-- 
Stephane