Do not allow msize in inline assembly if the Yul optimizer is active.

test/libsolidity/syntaxTests/inlineAssembly/use_msize_with_optimizer.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() pure public {
+        assembly {
+            let x := msize()
+        }
+    }
+}
+// ====
+// optimize-yul: true
+// ----
+// Warning: The Yul optimiser is still experimental. Do not use it in production unless correctness of generated code is verified with extensive tests.
+// SyntaxError: (52-101): The msize instruction cannot be used when the Yul optimizer is activated because it can change its semantics. Either disable the Yul optimizer or do not use the instruction.

test/libsolidity/syntaxTests/inlineAssembly/use_msize_without_optimizer.sol

@@ -0,0 +1,8 @@
+contract C {
+    function f() pure public {
+        assembly {
+            let x := msize()
+        }
+    }
+}
+// ----