Function minitt::check::tcm::update_gamma_by_pair

fn update_gamma_by_pair<'a>(
    gamma: Gamma<'a>, 
    pattern_first: &Box<Pattern>, 
    pattern_second: &Box<Pattern>, 
    first: Value, 
    second: Closure, 
    generated_val: Value
) -> TCM<Gamma<'a>>

Some minor helper specialized from other functions.