Integer add with carry instructions.

Integer addition with carry in/out/both.

cranelift/filetests/parser/ternary.cton

@@ -0,0 +1,13 @@
+test cat
+test verifier
+
+function add_i96(i32, i32, i32, i32, i32, i32) -> i32, i32, i32 {
+ebb1(v1: i32, v2: i32, v3: i32, v4: i32, v5: i32, v6: i32):
+    v10, v11 = iadd_cout v1, v4
+    ;check: $v10, $v11 = iadd_cout $v1, $v4
+    v20, v21 = iadd_carry v2, v5, v11
+    ; check: $v20, $v21 = iadd_carry $v2, $v5, $v11
+    v30 = iadd_cin v3, v6, v21
+    ; check: $v30 = iadd_cin $v3, $v6, $v21
+    return v10, v20, v30
+}