ELF Tool Chain Code

Do not modify the Elf_Data->d_buf buffer directly when applying
Elf_Rela relocation records, allocate another buffer to hold the
modified section data instead. The benefit is that when application is
sharing the ELF descriptor with libdwarf, it will have untouched
Elf_Data buffers.

* Added a 64bit (amd64) relocatable object which contains Elf_Rela
relocations records for DWARF debugging sections.
* Added "64bit .o" IC for a few test cases to test whether libdwarf handles
Elf_Rela correctly.

* Add global flag `applyrela` which controls whether libdwarf applies Elf_Rela
relocation records for DWARF debugging section before parsing. The flag is set
to 1 by default.
* Implement SGI libdwarf API dwarf_set_reloc_application() which is used to
set/clear the `applyrela` global flag.

Export elftc_bfd_target_byteorder() and elftc_bfd_target_flavor() in
Version.map

Implement new SGI libdwarf API dwarf_get_form_class(). This function
returns the DWARF form class provided DWARF spec version, attribute
number, DWARF offset size and DWARF form.

Add dwarf_ranges_dealloc.3 to MLINKS.

Document `dwarf_ranges_dealloc()`.

Submitted by: kaiwang27

Add test cases for abbrev, pubnames, macinfo and ranges consumer APIs.

Write escape sequence instead of literal character for those "special"
chars in XML. (<, >, &, ", etc)

Added two test objects which were compiled with gcc -g3. Among other
things, "gcc -g3" generates .debug_macinfo section.