Add borrow to stdlib and use ToOwned in impl_ops_add

Author: akubera

src/impl_ops_add.rs

@@ -2,6 +2,7 @@
 //!
 
 use super::*;
+use stdlib::borrow::ToOwned;
 
 
 impl Add<BigDecimal> for BigDecimal {

src/with_std.rs

@@ -25,4 +25,5 @@ mod stdlib {
     pub use std::collections::hash_map::DefaultHasher;
 
     pub use std::vec::Vec;
+    pub use std::borrow;
 }

src/without_std.rs

@@ -33,6 +33,7 @@ mod stdlib {
     #[cfg(test)]
     pub use siphasher::sip::SipHasher as DefaultHasher;
 
+    pub use alloc::borrow;
     pub use alloc::string;
     pub use alloc::vec::Vec;
 }