gc: allow ~ in import paths Windows has paths like C:/Users/ADMIN~1. Also, it so happens that go/parser allows ~ in import paths. So does the spec. Fixes the build too.
gc: allow ~ in import paths
Windows has paths like C:/Users/ADMIN~1. Also, it so happens
that go/parser allows ~ in import paths. So does the spec.
Fixes the build too.

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/5777073

wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old