Enables the use of custom key modifiers that repeat(e.g. Space, ⇥)
for use in tweak keymaps.

Problem
A key repeat event would end the tweak. This was not an issue with ⇧,
Control and Alt that typically do not repeat; but prevented the use
of regular key when used as modifier key for a tweak, except for a very short
time, until the first repeat.

Use case with problem:
Space + Alt + left mouse button move up for view3d.view_axis top

Solution
Check if an event is repeating.
A repeating event should always be press type, never a cause to cancel a tweak.