Allow toggling integer display signed-ness with `-`

[jonpalmisc]

The - hotkey can toggle the signed-ness of an integer data variable. It would also be handy if it could toggle the display signed-ness of integer tokens in linear/graph view.

[jonpalmisc]

Adding some more context and shamelessly bumping this: I notice Binary Ninja guessing the sign incorrectly a lot when analyzing kernels that are located at high addresses.