1) removed unused function, PcStoreOffset;
2) use macro instruction, Jump, when branching from JS code to C code.

This CL replaces http://codereview.chromium.org/53039/show, per our discussion.

Review URL: http://codereview.chromium.org/42610

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1614 ce2b1a6d-e550-0410-aec6-3dcde31c8c00