Ghost int literal

[arnaudgolfouse]

Create Ints in ghost code using a int suffix, like so:

ghost! {
    let x = 1int;
};

This is also added in pearlite for consistency.

Fixes #1251.

[arnaudgolfouse]

I'm unhappy about the duplicated ghost.rs file in creusot-contracts-proc and creusot-contracts-dummy, but using a #[path = "..."] annotation does not work... If someone has a better idea I'm interested!

[arnaudgolfouse]

I'm unhappy about the duplicated ghost.rs file in creusot-contracts-proc and creusot-contracts-dummy, but using a #[path = "..."] annotation does not work... If someone has a better idea I'm interested!

Well apparently it does work!