Fix the heap profiler crash caused by memory layout changes between passes.

Fix Error.prototype.toString to throw TypeError. (issue 1980)

Fix double-rounding in strtod for MinGW. (issue 1062)

Fix corrupted snapshot serializaton on ia32. (Chromium issue v8/1985)

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@10930 ce2b1a6d-e550-0410-aec6-3dcde31c8c00