Remove unused imports (#1426)

These are breaking the build on the latest `stable`

Author: tarcieri

cipher/src/dev/block.rs

@@ -1,7 +1,5 @@
 //! Development-related functionality
 
-pub use blobby;
-
 /// Define block cipher test
 #[macro_export]
 macro_rules! block_cipher_test {

digest/src/dev.rs

@@ -9,7 +9,6 @@ mod variable;
 mod xof;
 
 pub use fixed::*;
-pub use mac::*;
 pub use variable::*;
 pub use xof::*;