primitives: Re-export everything from units

We recently decided to make everything in `units` available at the same
path as in `primitives` and not re-export the actual `units` crate.

Re-export everything from the `units` crate root at the `primitives`
crate root using a wildcard.

primitives/src/lib.rs

@@ -32,6 +32,9 @@ pub mod locktime;
 pub mod opcodes;
 pub mod sequence;
 
+#[doc(inline)]
+pub use units::*;
+
 #[doc(inline)]
 #[cfg(feature = "alloc")]
 pub use self::locktime::{absolute, relative};