glib: Implement glib::StrV for NULL-terminated string arrays

Also comes with a `IntoStrV` trait that allows to borrow as a
`NULL`-terminated string array efficiently for various types.

Author: sdroege

glib/src/collections/mod.rs

@@ -11,3 +11,6 @@ pub use list::List;
 
 pub mod slist;
 pub use slist::SList;
+
+pub mod strv;
+pub use strv::{StrV, StrVItem};