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/tt.po

@@ -170,19 +170,19 @@ msgstr ""
 #: ../glib/gdatetime.c:207
 msgctxt "GDateTime"
 msgid "%a %b %e %H:%M:%S %Y"
-msgstr ""
+msgstr "%a %d %b %Y %T"
 
 #. 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
@@ -193,37 +193,37 @@ msgstr ""
 #: ../glib/gdatetime.c:229
 msgctxt "full month name"
 msgid "January"
-msgstr ""
+msgstr "Января"
 
 #: ../glib/gdatetime.c:231
 msgctxt "full month name"
 msgid "February"
-msgstr ""
+msgstr "Февраля"
 
 #: ../glib/gdatetime.c:233
 msgctxt "full month name"
 msgid "March"
-msgstr ""
+msgstr "Марта"
 
 #: ../glib/gdatetime.c:235
 msgctxt "full month name"
 msgid "April"
-msgstr ""
+msgstr "Апреля"
 
 #: ../glib/gdatetime.c:237
 msgctxt "full month name"
 msgid "May"
-msgstr ""
+msgstr "Мая"
 
 #: ../glib/gdatetime.c:239
 msgctxt "full month name"
 msgid "June"
-msgstr ""
+msgstr "Июня"
 
 #: ../glib/gdatetime.c:241
 msgctxt "full month name"
 msgid "July"
-msgstr ""
+msgstr "Июля"
 
 #: ../glib/gdatetime.c:243
 msgctxt "full month name"
@@ -253,37 +253,37 @@ msgstr ""
 #: ../glib/gdatetime.c:266
 msgctxt "abbreviated month name"
 msgid "Jan"
-msgstr ""
+msgstr "Янв"
 
 #: ../glib/gdatetime.c:268
 msgctxt "abbreviated month name"
 msgid "Feb"
-msgstr ""
+msgstr "Фев"
 
 #: ../glib/gdatetime.c:270
 msgctxt "abbreviated month name"
 msgid "Mar"
-msgstr ""
+msgstr "Мар"
 
 #: ../glib/gdatetime.c:272
 msgctxt "abbreviated month name"
 msgid "Apr"
-msgstr ""
+msgstr "Апр"
 
 #: ../glib/gdatetime.c:274
 msgctxt "abbreviated month name"
 msgid "May"
-msgstr ""
+msgstr "Май"
 
 #: ../glib/gdatetime.c:276
 msgctxt "abbreviated month name"
 msgid "Jun"
-msgstr ""
+msgstr "Июн"
 
 #: ../glib/gdatetime.c:278
 msgctxt "abbreviated month name"
 msgid "Jul"
-msgstr ""
+msgstr "Июл"
 
 #: ../glib/gdatetime.c:280
 msgctxt "abbreviated month name"
@@ -313,72 +313,72 @@ msgstr ""
 #: ../glib/gdatetime.c:303
 msgctxt "full weekday name"
 msgid "Monday"
-msgstr ""
+msgstr "Дышәмбе"
 
 #: ../glib/gdatetime.c:305
 msgctxt "full weekday name"
 msgid "Tuesday"
-msgstr ""
+msgstr "Сишәмбе"
 
 #: ../glib/gdatetime.c:307
 msgctxt "full weekday name"
 msgid "Wednesday"
-msgstr ""
+msgstr "Чәршәәмбе"
 
 #: ../glib/gdatetime.c:309
 msgctxt "full weekday name"
 msgid "Thursday"
-msgstr ""
+msgstr "Пәнҗешмбе"
 
 #: ../glib/gdatetime.c:311
 msgctxt "full weekday name"
 msgid "Friday"
-msgstr ""
+msgstr "Җомга"
 
 #: ../glib/gdatetime.c:313
 msgctxt "full weekday name"
 msgid "Saturday"
-msgstr ""
+msgstr "Шимбә"
 
 #: ../glib/gdatetime.c:315
 msgctxt "full weekday name"
 msgid "Sunday"
-msgstr ""
+msgstr "Якшәмбе"
 
 #: ../glib/gdatetime.c:330
 msgctxt "abbreviated weekday name"
 msgid "Mon"
-msgstr ""
+msgstr "Дыш"
 
 #: ../glib/gdatetime.c:332
 msgctxt "abbreviated weekday name"
 msgid "Tue"
-msgstr ""
+msgstr "Сиш"
 
 #: ../glib/gdatetime.c:334
 msgctxt "abbreviated weekday name"
 msgid "Wed"
-msgstr ""
+msgstr "Чәрш"
 
 #: ../glib/gdatetime.c:336
 msgctxt "abbreviated weekday name"
 msgid "Thu"
-msgstr ""
+msgstr "Пәнҗ"
 
 #: ../glib/gdatetime.c:338
 msgctxt "abbreviated weekday name"
 msgid "Fri"
-msgstr ""
+msgstr "Җом"
 
 #: ../glib/gdatetime.c:340
 msgctxt "abbreviated weekday name"
 msgid "Sat"
-msgstr ""
+msgstr "Шим"
 
 #: ../glib/gdatetime.c:342
 msgctxt "abbreviated weekday name"
 msgid "Sun"
-msgstr ""
+msgstr "Якш"
 
 #: ../glib/gdir.c:115 ../glib/gdir.c:138
 #, c-format