polish the GLError object

Author: gre

lib/GLError.js

@@ -1,5 +1,4 @@
 function GLError (rawError, shortMessage, longMessage) {
-    this.name = 'GLError'
     this.shortMessage = shortMessage || ''
     this.longMessage = longMessage || ''
     this.rawError = rawError || ''
@@ -9,4 +8,6 @@ function GLError (rawError, shortMessage, longMessage) {
     this.stack = (new Error()).stack
 }
 GLError.prototype = new Error
+GLError.prototype.name = 'GLError'
+GLError.prototype.constructor = GLError
 module.exports = GLError