- elf_getdata() and elf_rawdata() should return an "Elf_Data" structure
that has its "d_buf" member set to NULL and "d_size" member set to
the nominal 'size' of the section. [1]
- Update the manual page for these functions.
- Fix a memory leak in an error handling path inside elf_getdata().
- Use _libelf_allocate_data() in elf_newdata() for consistency.
Obtained from: elftoolchain
MFC after: 1 month
