fix mysql column constant typo occuring on AR 3.1
update postgres types tests - not sure how these pass in native adapter ...
but they seems to be expected to work the way these changes update'em
disable logger support - we do not want to see error msgs in case expected
+ less warning noise on 4.0
update test-unit-context - no 'ambigious' warning
[postgres] quoting that uses column.type (thus works with defs as well)
only use #sql_type when necessary (ColumnDefinition does not have it)
make a few (mysql) tests compatible when running against 4.0
[db2] separate AS400 code into a module + stadalone connection method