This consists mostly of making `public` types in the `Castle.Dynamic-
Proxy` namespace `internal`, however there are a few special cases
where types are left public but some or most of their members are made
internal, for example:

 * exception types (client code should be able to catch them, but not
   instantiate them)

 * `TypeUtil` (proxies require some of its members at runtime)

 * `ModuleScope` (`SaveAssembly`, `LoadAssemblyIntoCache`, and related
   members should stay public for now, unlike others that give access
   to the internal `ModuleBuilder`)

 * Windsor needs `TypeUtil.GetAllInterfaces`, so make it public again.

 * Windsor is currently relying on `DelegateProxyGenerator`, but there
   is now another, more public API to build delegate proxies (see PR
   castleproject#436) so that class can
   now be removed. The unit tests for it are rewritten in terms of the
   newer API to demonstrate that it is indeed a suitable replacement.

It is no longer feasible to list every single affected type or type
member; there's simply too many. Give a coarse summary instead.