Made a slight behavioral change in the ``sqlalchemy.ext.compiler``
extension, whereby the existing compilation schemes for an established
construct would be removed if that construct was itself didn't already
have its own dedicated ``__visit_name__``.  This was a
rare occurrence in 1.0, however in 1.1 :class:`.postgresql.ARRAY`
subclasses :class:`.sqltypes.ARRAY` and has this behavior.
As a result, setting up a compilation handler for another dialect
such as SQLite would render the main :class:`.postgresql.ARRAY`
object no longer compilable.

Fixes: #3732
Change-Id: If2c1ada4eeb09157885888e41f529173902f2b49

compilation rule which allows skipping of columns, by producing
a rule that returns ``None``.  Also in 0.8.3.

become an externally usable package but still remains within the main sqlalchemy parent package.
in this system, we use kind of an ugly hack to get the noseplugin imported outside of the
"sqlalchemy" package, while still making it available within sqlalchemy for usage by
third party libraries.

CREATE TABLE that provides access to the render for each
Column individually, by constructing a @compiles
function against the new schema.CreateColumn
construct.  [ticket:2463]

plain names.  The old names are still defined for
backwards compatibility.
- _BindParamClause renamed to BindParameter

informative error message when no "default"
compilation handler is present, rather
than KeyError.

- have "packagenames" be present on FunctionElement by default
so that compiler.visit_function() can be called
- add a test for that