build: build more packages/commands for Plan 9

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/4921041

src/pkg/Makefile

@@ -189,29 +189,7 @@ endif
 
 ifeq ($(GOOS),plan9)
 NOPLAN9BUILD=\
-	crypto/tls\
-	exp/gui/x11\
-	expvar\
-	http\
-	http/cgi\
-	http/fcgi\
-	http/httptest\
-	http/pprof\
-	http/spdy\
-	mail\
-	mime/multipart\
-	net\
-	net/dict\
-	net/textproto\
-	netchan\
 	os/signal\
-	rpc\
-	rpc/jsonrpc\
-	smtp\
-	syslog\
-	websocket\
-	../cmd/godoc\
-	../cmd/goinstall\
 
 DIRS:=$(filter-out $(NOPLAN9BUILD),$(DIRS))
 endif

src/pkg/os/error_plan9.go

@@ -48,6 +48,7 @@ var (
 	EPERM   = Eperm
 	EISDIR  = syscall.EISDIR
 
+	EBADF        = NewError("bad file descriptor")
 	ENAMETOOLONG = NewError("file name too long")
 	ERANGE       = NewError("math result not representable")
 	EPIPE        = NewError("Broken Pipe")