Add verbatim builtin.

test/libsolidity/syntaxTests/inlineAssembly/verbatim_disallowed.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() pure public {
+        assembly {
+            let x := verbatim_1o(hex"6001")
+        }
+    }
+}
+// ====
+// optimize-yul: true
+// ----
+// DeclarationError 4619: (84-95): Function "verbatim_1o" not found.
+// DeclarationError 3812: (75-106): Variable count mismatch for declaration of "x": 1 variables and 0 values.