Multiple locales: Add date_fmt (bug 24054)

It is not specified what should be the content of d_t_fmt and date_fmt
but in the built-in C locale those fields have only one difference:
date_fmt contains "%Z" (the current time zone) while d_t_fmt does not.

For most of the locales this commit does the following operation:
copy d_t_fmt to date_fmt, and then remove "%Z" from d_t_fmt.
If "%Z" was originally missing from d_t_fmt add it to date_fmt.
It also corrects comments where necessary.

Exceptions:

* In bo_CN, dz_BT, and km_KH "%Z" has not been added to date_fmt because
  it was too difficult.  In these locales date_fmt has been set to the
  copy of d_t_fmt.
* In en_DK "%Z" has not been removed from d_t_fmt in order to preserve
  the conformance with the standard mentioned in the comment.

The command to identify and initially edit the locales that need the
update was:

    for i in `grep -lw d_t_fmt *`
    do
        if ! grep -qw date_fmt $i ; then
            awk '/d_t_fmt/ { print $0; gsub("d_t_fmt", "date_fmt"); } //{ print $0 }' < $i > $i.next
            mv $i.next $i
        fi
    done

and then each file was further edited manually.

1 files changed, 3 insertions, 0 deletions

diff --git a/localedata/locales/en_SG b/localedata/locales/en_SG
index 5271c5b..0d8590b 100644
--- a/localedata/locales/en_SG
+++ b/localedata/locales/en_SG
@@ -123,6 +123,9 @@ am_pm       "AM";"PM"
 % Appropriate date and time representation
 d_t_fmt     "%a %d %b %Y %r"
 %
+% Appropriate date and time representation for date(1)
+date_fmt    "%a %d %b %Y %r %Z"
+%
 % Appropriate date representation
 d_fmt       "%d//%m//%Y"
 %