Fixed some IE issues

Fixed two IE issues:

1) The log() function was being declared and invoked in a way that was
breaking IE. Some calls were being made to ADL.XAPIWrapper.log() before
ADL.XAPIWrapper was fully instantiated. Fixed by declaring log() as a
local variable [within the closure's scope] and updating all callers to
access it directly, rather than as a property of XAPIWrapper.

2) Fixed a problem in getbase(). In some cases [maybe if you call the
page without any LRS config properties?] we end up assigning undefined
to a link's "href" property. Chrome and IE handle this differently and
in IE it was causing an error.