Large iterator refactoring, needed for some changes in the anonymous methods

Large iterator refactoring, needed for some changes in the anonymous methods
support.   What started as an innocent 10-line patch turned into a big
witch hunt.

2004-04-14  Miguel de Icaza  <miguel@ximian.com>

	* expression.cs (This.Emit): Use EmitContext.EmitThis to emit our
	instance variable.

	(This.EmitAssign): Ditto.

	* ecore.cs (FieldExpr.Emit): Remove RemapToProxy special
	codepaths, we will move all the functionality into
	Mono.CSharp.This

	(FieldExpr.EmitAssign): Ditto.

	This fixes several hidden bugs that I uncovered while doing a code
	review of this today.

	* codegen.cs (EmitThis): reworked so the semantics are more clear
	and also support value types "this" instances.

	* iterators.cs: Changed so that for iterators in value types, we
	do not pass the value type as a parameter.

	Initialization of the enumerator helpers is now done in the caller
	instead of passing the parameters to the constructors and having
	the constructor set the fields.

	The fields have now `assembly' visibility instead of private.

svn path=/trunk/mcs/; revision=25513