pub fn expand(
    cap: &[u8],
    params: &[Param],
    vars: &mut Variables
) -> Result<Vec<u8>, Error>Expand description
Expand a parameterized capability
Arguments
- cap- string to expand
- params- vector of params for %p1 etc
- vars- Variables struct for %Pa etc
To be compatible with ncurses, vars should be the same between calls to expand for
multiple capabilities for the same terminal.