Create 'type' annotation for 'const' variables

From https://developers.google.com/closure/compiler/docs/js-for-compiler:
  "The type declaration and additional comment are optional. If you
  provide a type declaration, put the declaration on a separate line."

src/ol/proj/proj.js

@@ -19,7 +19,8 @@ ol.ENABLE_PROJ4JS = true;
 
 /**
  * Have Proj4js.
- * @const {boolean}
+ * @const
+ * @type {boolean}
  */
 ol.HAVE_PROJ4JS = ol.ENABLE_PROJ4JS && typeof Proj4js == 'object';
 
@@ -47,7 +48,8 @@ ol.proj.Units = {
 
 /**
  * Meters per unit lookup table.
- * @const {Object.<ol.proj.Units, number>}
+ * @const
+ * @type {Object.<ol.proj.Units, number>}
  */
 ol.METERS_PER_UNIT = {};
 ol.METERS_PER_UNIT[ol.proj.Units.DEGREES] =