* MoonIsolatedStorageFile.cs: Return true, instead of throwing a NIE,
for IsEnabled since this is the behavior for Silverlight 3 (i.e. always
enabled) even if the call is new in SL4 (but part of ML3 ;-)

	* appdomain.c (unload_thread_main): Call function
	bindings cleanup.

	* assembly.c (mono_assembly_apply_binding): Dupe the
	content of per-domain bindings. Assign a domain_id on
	such entries to be possible to track them later.

	* assembly.c (mono_assembly_cleanup_domain_bindings):
	New function that removes per-domain bindings on
	unload.

	* metadata-internals.h (MonoAssemblyBindingInfo): Add
	domain_id field so it's possible to track if an entry
	is appdomain bound.