Better error-message when bind fails.

runtime/bin/socket_macos.cc

Index: runtime/bin/socket_macos.cc
diff --git a/runtime/bin/socket_macos.cc b/runtime/bin/socket_macos.cc
index 708cd3cdea9bd926079f611df3870980e8563d57..2e336a2003709fd5377c29f150d1f5b1a6aa7174 100644
--- a/runtime/bin/socket_macos.cc
+++ b/runtime/bin/socket_macos.cc
@@ -103,6 +103,12 @@ intptr_t Socket::CreateBindConnect(const RawAddr& addr,
 }
 
 
+bool Socket::IsBindError(intptr_t error_number) {
+  return error_number == EADDRINUSE || error_number == EADDRNOTAVAIL ||
+      error_number == EINVAL;
+}
+
+
 intptr_t Socket::Available(intptr_t fd) {
   return FDUtils::AvailableBytes(fd);
 }