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
likely to go back to registers for most temporaries.
most tests in lib pass. these fail:
datafmt
fmt
go/scanner
log
reflect
strconv
template
R=ken
OCL=29896
CL=29898
* string format changed
* files got renamed
* new files that i forgot to check in last time
updates are all copy and paste from 6g
R=ken
OCL=29385
CL=29400
