build: fprintftime/nstrftime API changes

build: fprintftime/nstrftime API changes

* bootstrap.conf (gnulib_modules): Add time_rz,
since the main source code now uses timezone_t.
* src/date.c (batch_convert, main, show_date):
* src/ls.c (align_nstrftime, long_time_expected_width)
(print_long_format):
* src/stat.c (human_time):
Use timezone_t rather than boolean to specify which time zone
is wanted.
* src/ls.c (localtz): New static var.
(main): Initialize it.