The loader package now loads, parses, and type-checks a whole program
from source, and that is all.
Also:
- simplified loader logic
- ssa.Create is gone; use ssautil.CreateProgram.
- ssautil.LoadPackage renamed to BuildPackage.
It is now independent of go/types' Import hook and the Packages map.
- ssadump: -importbin flag removed.
The value of this flag was that it caused the tool to print IR
for only a single package; this is now the normal behaviour.
Fixes#9955
Change-Id: I4571118258ab1a46dccece3241b7dc51401a3acc
Reviewed-on: https://go-review.googlesource.com/8953
Reviewed-by: Robert Griesemer <gri@golang.org>