Fix chaining carrying_adds

Something about the MIR lowering for `||` ended up breaking this, but it's fixed by changing the code to use `|` instead.

I also added an assembly test to ensure it *keeps* being `adc`.

Author: scottmcm

core/src/num/uint_macros.rs

@@ -2354,7 +2354,7 @@ macro_rules! uint_impl {
             //   to generate optimal code for now, and LLVM doesn't have an equivalent intrinsic
             let (a, b) = self.overflowing_add(rhs);
             let (c, d) = a.overflowing_add(carry as $SelfT);
-            (c, b || d)
+            (c, b | d)
         }
 
         /// Calculates `self` + `rhs` with a signed `rhs`.