Added missing docs for +support_migrations?+ on some adapters

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -214,6 +214,7 @@ def supports_statement_cache?
         true
       end
 
+      # Does MySQL support migrations?
       def supports_migrations? #:nodoc:
         true
       end

activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb

@@ -72,6 +72,7 @@ def supports_statement_cache?
         true
       end
 
+      # Does SQLite support migrations?
       def supports_migrations? #:nodoc:
         true
       end