add class for driver without prefix warning

+ some POD clarifying that

Author: rehsack

lib/DBI/DBD/SqlEngine.pm

@@ -97,7 +97,7 @@ EOI
     }
     else
     {
-        warn "Using DBI::DBD::SqlEngine with unregistered driver.\n"
+        warn "Using DBI::DBD::SqlEngine with unregistered driver $class.\n"
           . "Reading documentation how to prevent is strongly recommended.\n";
 
     }
@@ -1699,6 +1699,9 @@ Currently the API of DBI::DBD::SqlEngine is experimental and will
 likely change in the near future to provide the table meta data basics
 like DBD::File.
 
+DBI::DBD::SqlEngine expects that any driver in inheritance chain has
+a L<DBI prefix|DBI::DBD/The_database_handle_constructor>.
+
 =head2 Metadata
 
 The following attributes are handled by DBI itself and not by

lib/DBI/DBD/SqlEngine/HowTo.pod

@@ -30,8 +30,15 @@ L<DBI::DBD/CREATING A NEW DRIVER>.
 
 =head1 CREATING DRIVER CLASSES
 
-Do you have an entry in DBI's DBD registry? For this guide, a prefix of
-C<foo_> is assumed.
+Do you have an entry in DBI's DBD registry? DBI::DBD::SqlEngine expect
+having a unique prefix for every driver class in inheritance chain.
+
+It's easy to get a prefix - just drop the DBI team a note
+(L<DBI/GETTING_HELP>). If you want for some reason hide your work, take
+a look at L<Class::Method::Modifiers> how to wrap a private prefix method
+around existing C<driver_prefix>.
+
+For this guide, a prefix of C<foo_> is assumed.
 
 =head2 Sample Skeleton