introduce NodeList* type in compiler to replace OLIST.
this clarifies where lists can and cannot occur.
list append and concatenation are now cheap.
the _r rules are gone from yacc.
rev and unrev are gone.
no more lists of lists.

the representation of assignments is a bit clunkier.
split into OAS (1=1) and OAS2 (2 or more on one side).

delete dead chanrecv3 code.

delay construction of func types.

R=ken
OCL=31745
CL=31762