* CodeGen.cs: Fix tabbing

    * CodeGen.cs: Fix tabbing
	* ModifiableType.cs: Modify a types signature when the type is
	modified instead of waiting untill the end. Signatures need to be
	modified immediatly because they are used in method signatures and
	would fail for overloaded operations if sigs weren't modified
	right away.
	* ExternTypeRef.cs: Add signature modifications, fix some tabbing
	* GenericTypeInst.cs: Use ModifiableType as a base
	* GenericTypeRef.cs: Use ModifiableType as a base
	* PeapiTypeRef.cs: No longer take or modify type names.
	* PrimitiveTypeRef.cs: Add signature modifications, fix some tabbing.
	* Sentinel.cs: Add signature modifications, fix some tabbing.
	* TypeRef.cs: Add signature modifications, fix some tabbing.

svn path=/trunk/mcs/; revision=17231