libgo: Remove unnecessary EINTR checks.
libgo: Remove unnecessary EINTR checks.

We always use SA_RESTART with signals, so
read/write/etc. should never return EINTR.

R=iant
CC=gofrontend-dev
https://golang.org/cl/4325049

golang/gofrontend,golang/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend