parse-datetime: Support time zone names on MSVC.

* lib/parse-datetime.y (parse_datetime_body): Use HAVE_TZNAME_ARRAY
instead of HAVE_TZNAME. Don't declare tzname.
* modules/parse-datetime (Depends-on): Add tzname.
* m4/parse-datetime.m4 (gl_PARSE_DATETIME): Don't invoke
AC_STRUCT_TIMEZONE.

modules/parse-datetime

@@ -28,6 +28,7 @@ time-h
 time_r
 time_rz
 timegm
+tzname
 
 configure.ac:
 gl_PARSE_DATETIME