ExtendStorage did not work with keyed store IC.
- Reduced instructions generated when performing a tail call to 
  kSharedStoreIC_ExtendStorage
- Moved test/mjsunit/bugs/bug-109.js
  to test/mjsunit/keyed-storage-extend.js

Review URL: http://codereview.chromium.org/6526

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@455 ce2b1a6d-e550-0410-aec6-3dcde31c8c00