Move const PortName data out of header file

mojo/edk/system/ports/name.cc

Index: mojo/edk/system/ports/name.cc
diff --git a/mojo/edk/system/ports/name.cc b/mojo/edk/system/ports/name.cc
index 7088cbfd248e89c6ae51afd3f8292eb19e9fea18..ea17698f978c49eb60ae7833b7da57c1f6cfe9b7 100644
--- a/mojo/edk/system/ports/name.cc
+++ b/mojo/edk/system/ports/name.cc
@@ -8,6 +8,10 @@ namespace mojo {
 namespace edk {
 namespace ports {
 
+extern const PortName kInvalidPortName = {0, 0};
+
+extern const NodeName kInvalidNodeName = {0, 0};
+
 std::ostream& operator<<(std::ostream& stream, const Name& name) {
   std::ios::fmtflags flags(stream.flags());
   stream << std::hex << std::uppercase << name.v1;