R=golang-dev, rsc CC=golang-dev https://golang.org/cl/621041
- mkall now generates syscall stabs automatically - we can call unicode versions of winapi now - introduce GetErrstr function to fetch error text given errno - general cleanup R=rsc CC=golang-dev https://golang.org/cl/562041
lots of missing parts, but builds and can call dlls, see a sample code in syscall_mingw.go R=rsc CC=golang-dev https://golang.org/cl/218042
