)
Values DIET external procedure is called with:
	STACK:	WORD	class
			FFFDh creation failed for unknown reasons
			FFFEh creation failed due to lack of space
			FFFFh file creation error
			else file handle of DIETed file to be decompressed
		DWORD	-> compressed filename
		DWORD	-> decompressed or temporary filename
Return: SI,DI,BP,DS,ES must be preserved by external procedure