rpc/dataconn + build: support GOOS={solaris,illumos}

rpc/dataconn/timeoutconn/timeoutconn_readv_unsupported.go

@@ -0,0 +1,11 @@
+// +build illumos solaris
+
+package timeoutconn
+
+import "net"
+
+func (c Conn) readv(buffers net.Buffers) (n int64, err error) {
+	// Go does not expose the SYS_READV symbol for Solaris / Illumos - do they have it?
+	// Anyhow, use the fallback
+	return c.readvFallback(buffers)
+}