High memory usage -- duplication of data by segment and section

[sonals]

When reading an ELF section from a file or a stream, ELFIO copies the section data into its own storage, section_impl::data. However, ELFIO make another copy of the same data when it is reading the corresponding segment. This leads to doubling of memory usage which can be large for a large ELF file. I am wondering if a segment should just refer to data stored in the matching sections and duplicate the data only when segment_impl::get_data() is called?

[sonals]

PR #163 provides a solution.

[sonals]

Once the duplication of data by segment is resolved in #163 will look into adding support for mmap which should avoid copying of data even by sections.