Fix issue 571: display descriptive names for code objects from snapshot.

Fix issue 571: display descriptive names for code objects from snapshot.

As this is only needed for internal profiling (not for DevTools),
the following approach had been chosen:

 - during snapshot creation, positions of serialized objects inside
   a snapshot are logged;

 - then during V8 initialization, positions of deserealized objects
   are logged;

 - those positions are used for retrieving code objects names from
   snapshot creation log, which needs to be supplied to tick processor
   script.

Positions logging is controlled with the new flag: --log_snapshot_positions.
This flag is turned off by default, and this adds no startup penalty.

To plug this fix to Golem, the following actions are needed:

 - logs created using 'mksnapshot' need to be stored along with VM images;

 - tick processor script needs to be run with '--snapshot-log=...' cmdline
   argument.

BUG=571

Review URL: http://codereview.chromium.org/551062

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3635 ce2b1a6d-e550-0410-aec6-3dcde31c8c00