flag -l means: inlining on, -ll inline with early typecheck
-l lazily typechecks imports on use and re-export, nicer for debugging
-lm produces output suitable for errchk tests, repeated -mm... increases inl.c's verbosity
export processed constants, instead of originals
outparams get ->inlvar too, and initialized to zero
fix shared rlist bug, that lead to typecheck messing up the patched tree
properly handle non-method calls to methods T.meth(t, a...)
removed embryonic code to handle closures in inlined bodies
also inline calls inside closures (todo: move from phase 6b to 4)

Fixes #2579.

R=rsc
CC=golang-dev
https://golang.org/cl/5489106