fix some names in compare nil ic

The compare nil ic introduces a mechanism called lightweight miss. The
idea is to insert a direct call to the miss handler instead of going
through the deopt routine. This can be use for uninitialized stubs, to
directly jump to the runtime.

This cl
1. Cleans up naming
2. localizes the lightweight miss functionality on the only user (compare nil ic)
3. fixes DoCodegen, to actually call the correct method (uninitialized vs initialized)

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/15806005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14798 ce2b1a6d-e550-0410-aec6-3dcde31c8c00