Replicate signal names from syscall in os/signal.

R=rsc
CC=golang-dev
https://golang.org/cl/183142
diff --git a/.hgignore b/.hgignore
index c739a20..7e039d1 100644
--- a/.hgignore
+++ b/.hgignore
@@ -20,6 +20,7 @@
 src/cmd/gc/opnames.h
 src/pkg/Make.deps
 src/pkg/exp/ogle/ogle
+src/pkg/os/signal/unix.go
 src/pkg/runtime/cgo2c
 src/pkg/runtime/*/asm.h
 src/pkg/runtime/runtime.acid.*