Activated code aging by default.

Included more information in --prof log.

Removed eager sweeping for lazy swept spaces. Try to find in SlowAllocateRaw a bounded number of times a big enough memory slot. (issue 2194)

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@13101 ce2b1a6d-e550-0410-aec6-3dcde31c8c00