Added support in the profiler for creating 'regions' that cover part

Added support in the profiler for creating 'regions' that cover part
of the generated code.  These can be used by the profiler to
categorize the ticks that occur within generated code and thereby show
more detailed information about where time is spent in generated code.
For instance, this is what the profiler displayed for a simple regexp
benchmark with irregexp-native before:

[JavaScript]:
   total  nonlib   name
   87.2%   87.2%   RegExp: (?:\w*\W+)*

This is what we can display now:

[JavaScript]:
   total  nonlib   name
   87.2%   87.2%   RegExp: (?:\w*\W+)*
                   -  53.0%  56.7% BranchOrBacktrack
                   -  14.9%  59.8% CheckCharacterLT
                   -  13.7%  20.4% CheckStackLimit
                   -   6.7%   6.7% SafeCall
                   -   2.7%   7.0% CheckCharacterGT
                   -   2.4%   2.4% SafeReturn
                   -   2.1%   2.1% LoadCurrentCharacter
                   -   1.8%   1.8% PushRegister
                   -   0.9%   0.9% PopRegister
                   -   0.9%   0.9% AdvanceRegister
                   -   0.3%   0.3% PopCurrentPosition
                   -   0.3%   0.3% CheckGreedyLoop
                   -   0.0%  20.4% PushBacktrack
                   -   0.0%  22.3% CheckCharacter
                   -   0.0%   2.4% IfRegisterLT

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1010 ce2b1a6d-e550-0410-aec6-3dcde31c8c00