Fixes bug #15634. Eliminates compiler warning 'all return paths are recursive in

Field_date::store function'. Though the Field_date::store function almost unused
when protocol_version=10 additional check was added into it to store 4byte dates 
properly. Effective test routine is not available so far due to protocol_version
is not a dynamic property and can not be modified with mysql-test script.

sql/field.cc

@@ -5242,7 +5242,7 @@ int Field_date::store(double nr)
   else
     tmp= (longlong) rint(nr);
 
-  return Field_date::store(tmp);
+  return Field_date::store(tmp, TRUE);
 }
 
 
@@ -5264,6 +5264,9 @@ int Field_date::store(longlong nr, bool unsigned_val)
     error= 2;
   }
 
+  if (nr >= 19000000000000.0 && nr <= 99991231235959.0)
+    nr=floor(nr/1000000.0);			// Timestamp to date
+
   if (error)
     set_datetime_warning(MYSQL_ERROR::WARN_LEVEL_WARN,
                          error == 2 ? ER_WARN_DATA_OUT_OF_RANGE :