syscall: Don't define IPMreq in socket_irix.go.

From Rainer Orth.

From-SVN: r182549

libgo/go/syscall/socket_irix.go

@@ -74,17 +74,9 @@ func BindToDevice(fd int, device string) (err error) {
 	return ENOSYS
 }
 
-// struct ip_mreg is provived in <netinet/in.h>, but protected with _SGIAPI.
-// This could be enabled with -D_SGI_SOURCE, but conflicts with
-// -D_XOPEN_SOURCE=500 required for msg_control etc. in struct msghgr, so
-// simply provide it here.
-type IPMreq struct {
-	Multiaddr [4]byte
-	Interface [4]byte
-}
-
-// Similarly, <netdb.h> only provides struct addrinfo, AI_* and EAI_* if
-// _NO_XOPEN4 && _NO_XOPEN5.
+// <netdb.h> only provides struct addrinfo, AI_* and EAI_* if  _NO_XOPEN4
+// && _NO_XOPEN5, but -D_XOPEN_SOURCE=500 is required for msg_control etc.
+// in struct msghgr, so simply provide them here.
 type Addrinfo struct {
 	Ai_flags     int32
 	Ai_family    int32