hdf5_ep

Adding new C++ wrappers
Description:
    - Added wrappers for H5Tencode to class DataType and H5Tdecode to
      classes DataType and its subclasses.

        // Creates a binary object description of this datatype.
        void DataType::encode()

        // Returns the decoded type from the binary object description.
        virtual DataType* DataType::decode() const;
        virtual DataType* ArrayType::decode() const;
        virtual DataType* CompType::decode() const;
        virtual DataType* DataType::decode() const;
        virtual DataType* EnumType::decode() const;
        virtual DataType* FloatType::decode() const;
        virtual DataType* IntType::decode() const;
        virtual DataType* StrType::decode() const;
        virtual DataType* VarLenType::decode() const;

    - Replaced existing functions CommonFG::openXxxType with individual
      data type constructors, XxxType, to improve usability.

Platforms tested:
    Linux/32 2.6 (jam)
    Linux/64 (platypus)
    Darwin (osx1010test)