Deprecate prepare push commit when pushing to trunk.

- This also deprecates using version.cc on bleeding edge.
- The deprecated push-to-trunk.sh is deleted.
- The script now commits bleeding edge HEAD by default. Committing different revisions will be added in a follow up CL.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/203753010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20101 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Remove unnecessary 'explicit' attribute.

R=marja@chromium.org

Review URL: https://codereview.chromium.org/206183002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20104 ce2b1a6d-e550-0410-aec6-3dcde31c8c00