Reviewed by Maciej Stachowiak & Oliver Hunt.

        Add support for reusing temporary JSNumberCells.  This change is based on the observation
        that if the result of certain operations is a JSNumberCell and is consumed by a subsequent
        operation that would produce a JSNumberCell, we can reuse the object rather than allocating
        a fresh one.  E.g. given the expression ((a * b) * c), we can statically determine that
        (a * b) will have a numeric result (or else it will have thrown an exception), so the result
        will either be a JSNumberCell or a JSImmediate.

        This patch changes three areas of JSC:
            * The AST now tracks type information about the result of each node.
            * This information is consumed in bytecode compilation, and certain bytecode operations
              now carry the statically determined type information about their operands.
            * CTI uses the information in a number of fashions:
                * Where an operand to certain arithmetic operations is reusable, it will plant code
                  to try to perform the operation in JIT code & reuse the cell, where appropriate.
                * Where it can be statically determined that an operand can only be numeric (typically
                  the result of another arithmetic operation) the code will not redundantly check that
                  the JSCell is a JSNumberCell.
                * Where either of the operands to an add are non-numeric do not plant an optimized
                  arithmetic code path, just call straight out to the C function.

        +6% Sunspider (10% progression on 3D, 16% progression on math, 60% progression on access-nbody),
        +1% v8-tests (improvements in raytrace & crypto)

        * VM/CTI.cpp: Add optimized code generation with reuse of temporary JSNumberCells.
        * VM/CTI.h:
        * kjs/JSNumberCell.h:
        * masm/X86Assembler.h:

        * VM/CodeBlock.cpp: Add type information to specific bytecodes.
        * VM/CodeGenerator.cpp:
        * VM/CodeGenerator.h:
        * VM/Machine.cpp:

        * kjs/nodes.cpp: Track static type information for nodes.
        * kjs/nodes.h:
        * kjs/ResultDescriptor.h: (Added)
        * JavaScriptCore.xcodeproj/project.pbxproj:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@36976 268f45cc-cd09-0410-ab3c-d52691b4dbfc