[MlMt] Issues with custom key bindings

[John Purnell]

I have noticed that two of the standard custom key bindings (`MailMate.app/Contents/Resources/KeyBindings/Standard.plist`) don't work. These are:

1. `" " = "scrollPageDownOrNextMessage:";`, not even when changing `" "` to `"\U0020"`. It scrolls down, but doesn't move to the next message.
2. `"\U000D" = "openMessages:";`, but when changing `"\U000D"` to `"\U0003" it does work.

Also, the numeric key pad keys don't work when using the `"#1"` syntax, but do when using the `"\U0031"` unicode equivalent.

I was wondering if these issue were specific to me or if others also had encountered them.