Fix the --max-old-space-size flag so it can be used on 64 bit for

Fix the --max-old-space-size flag so it can be used on 64 bit for
multi-gigabyte heap sizes.  The unit is Mbytes.
Hurry the incremental GC when the mutator is mutating too fast for
the incremental marker to keep up.
Print the length of the longest marking step at the end of an
incremental mark-sweep GC.
Skip a Mozilla test that causes deliberate out of memory errors.
Committed: http://code.google.com/p/v8/source/detail?r=8861

[Vyacheslav Egorov (Chromium), 2011-08-09 09:16:23]

LGTM