parse-datetime no longer depends on nstrftime

I discovered this unnecessary dependency when debugging
GNU Patch.
* lib/parse-datetime.y:
(populate_local_time_zone_table) [!HAVE_STRUCT_TM_TM_ZONE]:
(debug_strfdatetime): Use strftime not nstrftime,
as we don’t need nstrftime’s extensions or bug fixes.
* modules/parse-datetime (Depends-on): Remove nstrftime.
Also remove setenv, unsetenv, timegm, as this module
no longer depends on them directly.

modules/parse-datetime

@@ -20,14 +20,10 @@ idx
 intprops
 inttypes
 mktime
-nstrftime
-setenv
 stdckdint
-unsetenv
 time-h
 time_r
 time_rz
-timegm
 
 configure.ac:
 gl_PARSE_DATETIME