In mcs and gmcs:

In mcs and gmcs:
	Implement parts of #77403
	* roottypes.cs (RootDeclSpace): New.  Used to represent the
	toplevel declaration space.  Each namespace declaration introduces
	a "partial" root declaretion space.
	* namespace.cs (NamespaceEntry.SlaveDeclSpace): New.
	(NamespaceEntry.ctor): Create a SlaveDeclSpace if necessary.
	* cs-parser.jay (CSharpParser.ctor): Initialize 'current_class'
	from 'current_namespace.SlaveDeclSpace'.
	(namespace_declaration): Likewise.
	* class.cs (TypeContainer.ctor): Remove parent==ToplevelTypes
	check.  It can't happen now.
	* decl.cs (DeclSpace.LookupType): Likewise.
	* driver.cs (MainDriver): Sanity check.

svn path=/trunk/mcs/; revision=63243