Added $wgLocalStylePath global variable, and solved bug #22858 by using this new...

Added $wgLocalStylePath global variable, and solved bug #22858 by using this new variable in the Vector skin for the inclusion of skins/vector/csshover.htc. HTC files are not cross-domain friendly, so in production environments where $wgStylePath is set to point to bits.wikimedia.org, this will throw JavaScript errors on the page. By adding this new global, which is identical to $wgStylePath except that it will not become customized when $wgStylePath is, we can ensure that certain files, if needed, are always loaded from the same domain as the site.