Remove unnecesssary auxiliary definitions.

R=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/413983005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22860 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Removed GetConstructor from the API.
Instead either get the "constructor" property stored in the prototype, or keep a side-table.

LOG=y
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/438303003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22861 ce2b1a6d-e550-0410-aec6-3dcde31c8c00