Assume C99-style ‘long long’

Assume C99-style ‘long long’

Now that Gnulib assumes ‘long long’, it is a good time to clean
out old cruft porting to pre-C99 compilers that lack it.
* src/data.c (ULL_WIDTH, ULL_MAX): Remove.
All uses replaced by ULLONG_WIDTH, ULLONG_MAX.
(bits_word_to_host_endian): Assume ‘unsigned long long’.
By the way, the old code had a performance typo: it used
HAVE_UNSIGNED_LONG_LONG where it should have used
HAVE_UNSIGNED_LONG_LONG_INT.
* src/sysdep.c (ULLONG_MAX): Remove, as lib/limits.h does this now.
(time_from_jiffies) [GNU_LINUX]: Assume ‘long long’.