Include "gettext.h".

Include "gettext.h".
(_): New macro.
(bitset_stats_set, bitset_stats_reset, bitset_stats_test): Don't
name locals "index", as it generates unnecessary warnings on some
hosts that have an "index" function.

(bitset_stats_print_1, bitset_stats_print, bitset_stats_read,
bitset_stats_write): Wrap strings in _() if they need translation.

(bitset_stats_set, bitset_stats_reset): Do not assume that bitset_word
is the same width as int.