don't move expressions containing the binary in operator into the for initializer

(opera can't parse it)

close #25

test/compress/sequences.js

@@ -127,3 +127,35 @@ lift_sequences_4: {
         x = baz;
     }
 }
+
+for_sequences: {
+    options = { sequences: true };
+    input: {
+        // 1
+        foo();
+        bar();
+        for (; false;);
+        // 2
+        foo();
+        bar();
+        for (x = 5; false;);
+        // 3
+        x = (foo in bar);
+        for (; false;);
+        // 4
+        x = (foo in bar);
+        for (y = 5; false;);
+    }
+    expect: {
+        // 1
+        for (foo(), bar(); false;);
+        // 2
+        for (foo(), bar(), x = 5; false;);
+        // 3
+        x = (foo in bar);
+        for (; false;);
+        // 4
+        x = (foo in bar);
+        for (y = 5; false;);
+    }
+}