Correct various things in rangy-position to make it work in IE

* Add semicolons at the end of statements where they were missing
* Do not conditionally define createDocumentBoundaryPosGetter(),
  jshint doesn't like that and the function is used outside of
  the block where it is defined

Fixing these things makes confusing errors in IE go away.

Change-Id: I18cc0abe23f649515e555cd9318f88bf91fc7ac1