Populate missing GDateTime format strings

Use the glibc locale database to add GDateTime strings only for those locales
that had not specifically added them for themselves.

Some locales have different translations from what is in the C library and we
leave those alone with this commit.

po/nds.po

@@ -172,19 +172,19 @@ msgstr ""
 #: ../glib/gdatetime.c:207
 msgctxt "GDateTime"
 msgid "%a %b %e %H:%M:%S %Y"
-msgstr ""
+msgstr "%a %d. %b %Y %T %Z"
 
 #. Translators: this is the preferred format for expressing the date
 #: ../glib/gdatetime.c:210
 msgctxt "GDateTime"
 msgid "%m/%d/%y"
-msgstr ""
+msgstr "%d.%m.%Y"
 
 #. Translators: this is the preferred format for expressing the time
 #: ../glib/gdatetime.c:213
 msgctxt "GDateTime"
 msgid "%H:%M:%S"
-msgstr ""
+msgstr "%T"
 
 #. Translators: this is the preferred format for expressing 12 hour time
 #: ../glib/gdatetime.c:216
@@ -195,37 +195,37 @@ msgstr ""
 #: ../glib/gdatetime.c:229
 msgctxt "full month name"
 msgid "January"
-msgstr ""
+msgstr "Jannuaar"
 
 #: ../glib/gdatetime.c:231
 msgctxt "full month name"
 msgid "February"
-msgstr ""
+msgstr "Feberwaar"
 
 #: ../glib/gdatetime.c:233
 msgctxt "full month name"
 msgid "March"
-msgstr ""
+msgstr "März"
 
 #: ../glib/gdatetime.c:235
 msgctxt "full month name"
 msgid "April"
-msgstr ""
+msgstr "April"
 
 #: ../glib/gdatetime.c:237
 msgctxt "full month name"
 msgid "May"
-msgstr ""
+msgstr "Mai"
 
 #: ../glib/gdatetime.c:239
 msgctxt "full month name"
 msgid "June"
-msgstr ""
+msgstr "Juni"
 
 #: ../glib/gdatetime.c:241
 msgctxt "full month name"
 msgid "July"
-msgstr ""
+msgstr "Juli"
 
 #: ../glib/gdatetime.c:243
 msgctxt "full month name"
@@ -255,37 +255,37 @@ msgstr ""
 #: ../glib/gdatetime.c:266
 msgctxt "abbreviated month name"
 msgid "Jan"
-msgstr ""
+msgstr "Jan"
 
 #: ../glib/gdatetime.c:268
 msgctxt "abbreviated month name"
 msgid "Feb"
-msgstr ""
+msgstr "Feb"
 
 #: ../glib/gdatetime.c:270
 msgctxt "abbreviated month name"
 msgid "Mar"
-msgstr ""
+msgstr "Mär"
 
 #: ../glib/gdatetime.c:272
 msgctxt "abbreviated month name"
 msgid "Apr"
-msgstr ""
+msgstr "Apr"
 
 #: ../glib/gdatetime.c:274
 msgctxt "abbreviated month name"
 msgid "May"
-msgstr ""
+msgstr "Mai"
 
 #: ../glib/gdatetime.c:276
 msgctxt "abbreviated month name"
 msgid "Jun"
-msgstr ""
+msgstr "Jun"
 
 #: ../glib/gdatetime.c:278
 msgctxt "abbreviated month name"
 msgid "Jul"
-msgstr ""
+msgstr "Jul"
 
 #: ../glib/gdatetime.c:280
 msgctxt "abbreviated month name"
@@ -315,72 +315,72 @@ msgstr ""
 #: ../glib/gdatetime.c:303
 msgctxt "full weekday name"
 msgid "Monday"
-msgstr ""
+msgstr "Maandag"
 
 #: ../glib/gdatetime.c:305
 msgctxt "full weekday name"
 msgid "Tuesday"
-msgstr ""
+msgstr "Dingsdag"
 
 #: ../glib/gdatetime.c:307
 msgctxt "full weekday name"
 msgid "Wednesday"
-msgstr ""
+msgstr "Middeweek"
 
 #: ../glib/gdatetime.c:309
 msgctxt "full weekday name"
 msgid "Thursday"
-msgstr ""
+msgstr "Dunnersdag"
 
 #: ../glib/gdatetime.c:311
 msgctxt "full weekday name"
 msgid "Friday"
-msgstr ""
+msgstr "Freedag"
 
 #: ../glib/gdatetime.c:313
 msgctxt "full weekday name"
 msgid "Saturday"
-msgstr ""
+msgstr "Sünnavend"
 
 #: ../glib/gdatetime.c:315
 msgctxt "full weekday name"
 msgid "Sunday"
-msgstr ""
+msgstr "Sünndag"
 
 #: ../glib/gdatetime.c:330
 msgctxt "abbreviated weekday name"
 msgid "Mon"
-msgstr ""
+msgstr "Maan"
 
 #: ../glib/gdatetime.c:332
 msgctxt "abbreviated weekday name"
 msgid "Tue"
-msgstr ""
+msgstr "Ding"
 
 #: ../glib/gdatetime.c:334
 msgctxt "abbreviated weekday name"
 msgid "Wed"
-msgstr ""
+msgstr "Migg"
 
 #: ../glib/gdatetime.c:336
 msgctxt "abbreviated weekday name"
 msgid "Thu"
-msgstr ""
+msgstr "Dunn"
 
 #: ../glib/gdatetime.c:338
 msgctxt "abbreviated weekday name"
 msgid "Fri"
-msgstr ""
+msgstr "Free"
 
 #: ../glib/gdatetime.c:340
 msgctxt "abbreviated weekday name"
 msgid "Sat"
-msgstr ""
+msgstr "Svd."
 
 #: ../glib/gdatetime.c:342
 msgctxt "abbreviated weekday name"
 msgid "Sun"
-msgstr ""
+msgstr "Sdag"
 
 #: ../glib/gdir.c:115 ../glib/gdir.c:138
 #, c-format