Add nocov markings around unused code only kept for backwards compati…

…bility

This methods are no longer used, but remain in case an external
adapter is using them.  They will be removed in Sequel 6.

lib/sequel/adapters/shared/postgres.rb

@@ -2150,10 +2150,14 @@ def supports_skip_locked?
         server_version >= 90500
       end
 
+      # :nocov:
+
       # PostgreSQL supports timezones in literal timestamps
       def supports_timestamp_timezones?
+        # SEQUEL6: Remove
         true
       end
+      # :nocov:
 
       # PostgreSQL 8.4+ supports WINDOW clause.
       def supports_window_clause?

lib/sequel/dataset/features.rb

@@ -188,10 +188,14 @@ def supports_select_all_and_column?
       true
     end
 
+    # :nocov:
+
     # Whether the dataset supports timezones in literal timestamps, false by default.
     def supports_timestamp_timezones?
+      # SEQUEL6: Remove
       false
     end
+    # :nocov:
 
     # Whether the dataset supports fractional seconds in literal timestamps, true by default.
     def supports_timestamp_usecs?

lib/sequel/dataset/sql.rb

@@ -1206,14 +1206,18 @@ def format_timestamp(v)
       db.from_application_timestamp(v).strftime(default_timestamp_format)
     end
 
+    # :nocov:
+
     # Return the SQL timestamp fragment to use for the fractional time part.
     # Should start with the decimal point.  Uses 6 decimal places by default.
     def format_timestamp_usec(usec, ts=timestamp_precision)
+      # SEQUEL6: Remove
       unless ts == 6
         usec = usec/(10 ** (6 - ts))
       end
       sprintf(".%0#{ts}d", usec)
     end
+    # :nocov:
 
     # Append literalization of identifier to SQL string, considering regular strings
     # as SQL identifiers instead of SQL strings.