-

Changes to be committed:
* new file:   samples/BTL.typer     	(list implementation)
* new file:   samples/autodiff.typer
	simple symbolic diff example
* src/lparse.ml:
	- improved lexp_decls (lexp_decls now lexp_p_check when it can)
	- handle Phas_type
	- lexp_p_check: handle Plambda
	- moved macro handling to lexp_p_check
* tests/eval_test.ml:
	- added list test
	- added necessary type annotations