Remove goog.asserts.*

This pull requests replaces type check hint assertions with type casts,
library sanity check assertions with conditional console.assert statements
in debug mode, and runtime sanity checks with assertions that throw an
ol.AssertionError with an error code for lookup outside the library.

src/ol/math.js

@@ -1,6 +1,5 @@
 goog.provide('ol.math');
 
-goog.require('goog.asserts');
 
 
 /**
@@ -48,7 +47,7 @@ ol.math.cosh = (function() {
  * @return {number} The smallest power of two greater than or equal to x.
  */
 ol.math.roundUpToPowerOfTwo = function(x) {
-  goog.asserts.assert(0 < x, 'x should be larger than 0');
+  ol.assert(0 < x, 29); // `x` must be greater than `0`
   return Math.pow(2, Math.ceil(Math.log(x) / Math.LN2));
 };
 
@@ -106,9 +105,9 @@ ol.math.squaredDistance = function(x1, y1, x2, y2) {
 ol.math.solveLinearSystem = function(mat) {
   var n = mat.length;
 
-  if (goog.asserts.ENABLE_ASSERTS) {
+  if (ol.DEBUG) {
     for (var row = 0; row < n; row++) {
-      goog.asserts.assert(mat[row].length == n + 1,
+      console.assert(mat[row].length == n + 1,
                           'every row should have correct number of columns');
     }
   }