Allow protocol to be separated from host with a semicolon

Some DHCP servers (such as dnsmasq) tokenise parameters with commas, making
it impossible to pass boot files with commas in them. Allow using a semicolon
to separate the protocol from host if a comma wasn't found.

grub-core/net/net.c

@@ -1280,6 +1280,10 @@ grub_net_open_real (const char *name)
       const char *comma;
       char *colon;
       comma = grub_strchr (name, ',');
+      if (!comma)
+	{
+	  comma = grub_strchr (name, ';');
+	}
       colon = grub_strchr (name, ':');
       if (colon)
 	{