fixes #69, avoid module name inside module scope

test/codegen/expect/math/math.js

 var math;
-(function(math) {
+(function(exports) {
   'use strict';
   let E = 2.718281828459045;
   let LN10 = 2.302585092994046;
   let LN2 = 0.6931471805599453;
   let LOG2E = 1.4426950408889634;
   let LOG10E = 0.4342944819032518;
   let PI = 3.141592653589793;
   let SQRT1_2 = 0.7071067811865476;
   let SQRT2 = 1.4142135623730951;
   // Function min: (num, num) → num
@@ skipping 396 matching lines @@
     dart.defineNamedConstructor(MutableRectangle, 'fromPoints');
     return MutableRectangle;
   });
   let MutableRectangle = MutableRectangle$(dynamic);
   // Function _clampToZero: (num) → num
   function _clampToZero(value) {
     dart.assert(dart.notNull(value) < 0);
     return dart.notNull(-dart.notNull(value)) * 0;
   }
   // Exports:
-  math.E = E;
-  math.LN10 = LN10;
-  math.LN2 = LN2;
-  math.LOG2E = LOG2E;
-  math.LOG10E = LOG10E;
-  math.PI = PI;
-  math.SQRT1_2 = SQRT1_2;
-  math.SQRT2 = SQRT2;
-  math.min = min;
-  math.max = max;
-  math.atan2 = atan2;
-  math.pow = pow;
-  math.sin = sin;
-  math.cos = cos;
-  math.tan = tan;
-  math.acos = acos;
-  math.asin = asin;
-  math.atan = atan;
-  math.sqrt = sqrt;
-  math.exp = exp;
-  math.log = log;
-  math.Point = Point;
-  math.Point$ = Point$;
-  math.Random = Random;
-  math.Rectangle = Rectangle;
-  math.Rectangle$ = Rectangle$;
-  math.MutableRectangle = MutableRectangle;
-  math.MutableRectangle$ = MutableRectangle$;
+  exports.E = E;
+  exports.LN10 = LN10;
+  exports.LN2 = LN2;
+  exports.LOG2E = LOG2E;
+  exports.LOG10E = LOG10E;
+  exports.PI = PI;
+  exports.SQRT1_2 = SQRT1_2;
+  exports.SQRT2 = SQRT2;
+  exports.min = min;
+  exports.max = max;
+  exports.atan2 = atan2;
+  exports.pow = pow;
+  exports.sin = sin;
+  exports.cos = cos;
+  exports.tan = tan;
+  exports.acos = acos;
+  exports.asin = asin;
+  exports.atan = atan;
+  exports.sqrt = sqrt;
+  exports.exp = exp;
+  exports.log = log;
+  exports.Point = Point;
+  exports.Point$ = Point$;
+  exports.Random = Random;
+  exports.Rectangle = Rectangle;
+  exports.Rectangle$ = Rectangle$;
+  exports.MutableRectangle = MutableRectangle;
+  exports.MutableRectangle$ = MutableRectangle$;
 })(math || (math = {}));