Add configureProj4jsProjection function

so that we can add extent and global parameter to proj4js projections.
And remove setExtent method which is not relevant.

src/ol/projection.exports

@@ -17,3 +17,4 @@
 @exportSymbol ol.projection.getTransformFromCodes
 @exportSymbol ol.projection.transform
 @exportSymbol ol.projection.transformWithCodes
+@exportSymbol ol.projection.configureProj4jsProjection

src/ol/projection.js

@@ -107,14 +107,6 @@ ol.Projection.prototype.getExtent = function() {
 };
 
 
-/**
- * @param {ol.Extent} extent Extent.
- */
-ol.Projection.prototype.setExtent = function(extent) {
-  this.extent_ = extent;
-};
-
-
 /**
  * @param {number} resolution Resolution.
  * @param {ol.Coordinate} point Point.
@@ -663,3 +655,14 @@ ol.projection.transformWithCodes =
   vertex = transformFn(vertex, vertex, 2);
   return new ol.Coordinate(vertex[0], vertex[1]);
 };
+
+
+/**
+ * @param {ol.Proj4jsProjectionOptions} options Projection config options.
+ * @return {ol.Proj4jsProjection_} Proj4js projection.
+ */
+ol.projection.configureProj4jsProjection = function(options) {
+  goog.asserts.assert(!goog.object.containsKey(
+      ol.projection.proj4jsProjections_, options.code));
+  return ol.projection.getProj4jsProjectionFromCode_(options);
+};