This CL adds support for ConstantPoolArrays which contain an extended section.
This will be used to enable larger constant pools than can be addressed by a
single ldr with immediate offset instruction (which has a limit of a 4KB range).
Extended constant pools will have a small section, which is addressable via a
single ldr instruction, and an extended section, which will require a multi-
instruction sequence to load from.

Currently, no code uses the extended ConstantPoolArray's - this change will
be made in a followup CL.

A number of changes are made to the ConstantPoolArray object in order to
support this:
  - Small section layout is now entirely defined by the small layout bitmaps.
  - The ConstantPoolArray no longer extends FixedArrayBase since the length
    field is not useful for extended layouts.
  - Enums are used to represent the type of an entry and the layout section.
  - An iterator can be used to iterate through all elements of a given type.
  - A number of tests were added for these features.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/304143002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21653 ce2b1a6d-e550-0410-aec6-3dcde31c8c00