Also copy over cputicks.go, env_posix.go, vdso_none.go, stubs2.go, and a
part of os_linux.go. Remove the corresponding functions from the C code
in libgo/go/runtime. Add some transitional support functions to
stubs.go. This converts several minor functions from C to Go.
Reviewed-on: https://go-review.googlesource.com/29962
From-SVN: r240609
