Remove %_SwapElements.  This inlined runtime contained an optimization that was dangerous in the presence of incremental compaction.  It also prevented QuickSort from array.js from being optimized by Crankshaft, so it is probably better to do without it.  We have high hopes that this will fix bug=117879.
Review URL: https://chromiumcodereview.appspot.com/10392150

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11588 ce2b1a6d-e550-0410-aec6-3dcde31c8c00