[BUG] Broken build with 0.16.3

**Describe the bug**

**To Reproduce**
Create new bin and add
[dependencies]
cursive = "0.16.3"

error[E0310]: the parameter type `F` may not live long enough
-->/.cargo/registry/src/github.com-1ecc6299db9ec823/cursive_core-0.2.2/src/cursive.rs:650:19
|
645 | pub fn set_on_post_event(&mut self, trigger: E, cb: F)
| - help: consider adding an explicit lifetime bound...: `F: 'static`
...
650 | self.root.set_on_event(trigger, crate::immut1!(cb));
| ^^^^^^^^^^^^ ...so that the type `[closure@/.cargo/registry/src/github.com-1ecc6299db9ec823/cursive_core-0.2.2/src/utils/immutify.rs:87:9: 92:10]` will meet its required lifetime bounds

**Environment**
* Ubuntu
* Backend used: ncurses (the default one),
* Current locale en_US
* Cursive version (from crates.io)