- ParseFile (core of go/loader's parseFiles(); also used by refactor/rename)
- ContainingPackage (core of Oracle's guessImportPath; also used by refactor/rename)
- Accessors for effective "methods" of build.Context:
FileExists, OpenFile, IsAbsPath, JoinPath.
LGTM=sameer
R=dave, sameer
CC=golang-codereviews, gri
https://golang.org/cl/146120043