Extend __libdw_open_file and elf_begin as *_at_offset.

Extend __libdw_open_file and elf_begin as *_at_offset.

./
2014-02-22  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Extend __libdw_open_file and elf_begin as *_at_offset.
	* NEWS (libelf): New, with elf_begin_at_offset.

libdwfl/
2014-02-22  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Extend __libdw_open_file and elf_begin as *_at_offset.
	* libdwflP.h (__libdw_open_file_at_offset): New declaration.
	* open.c (__libdw_open_file): Rename to ...
	(__libdw_open_file_at_offset): ... here and add parameters start_offset
	and maximum_size.
	(__libdw_open_file): New wrapper of it.

libelf/
2014-02-22  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Extend __libdw_open_file and elf_begin as *_at_offset.
	* elf_begin.c (elf_begin): Rename to ...
	(elf_begin_at_offset): ... here and add parameters start_offset and
	maximum_size.
	(elf_begin): New wrapper of it.
	* libelf.h (elf_begin_at_offset): New declaration.
	* libelf.map (ELFUTILS_1.7): New, with elf_begin_at_offset.

Signed-off-by: Jan Kratochvil <jan.kratochvil@redhat.com>