Misc: remove function of disabling 'alt + click' on a link

* This has been supported by default in Fx 13.
  See https://developer.mozilla.org/en/docs/Mozilla/Preferences/Preference_reference/browser.altClickSave

* I implemented this function for selecting text inside of a link.
  See https://bugzilla.mozilla.org/show_bug.cgi?id=378775
WebService: improve XMLHttpRequest handler

* store the request time for each host
* define as the static handler: use 'const' and name with initial capital
  letter