This is a just a file move with no other changes
besides the manual import path adjustments in these
two files:

src/pkg/exp/gotype/gotype.go
src/pkg/exp/gotype/gotype_test.go

Note: The go/types API continues to be subject to
possibly significant changes until Go 1.1. Do not
rely on it being stable at this point.

R=adonovan
CC=golang-dev
https://golang.org/cl/7013049