x86: Add _bfd_x86_elf_adjust_dynamic_symbol

x86: Add _bfd_x86_elf_adjust_dynamic_symbol

Share _bfd_x86_elf_adjust_dynamic_symbol in elf32-i386.c and
elf64-x86-64.c.

	* elf32-i386.c (elf_i386_adjust_dynamic_symbol): Removed.
	(elf_backend_adjust_dynamic_symbol): Likewise.
	* elf64-x86-64.c (elf_x86_64_adjust_dynamic_symbol): Likewise.
	(elf_backend_adjust_dynamic_symbol): Likewise.
	* elfxx-x86.c (_bfd_x86_elf_adjust_dynamic_symbol): New function.
	(_bfd_x86_elf_link_setup_gnu_properties): Copy is_vxworks.
	* elfxx-x86.h (elf_x86_link_hash_table): Add is_vxworks.
	(_bfd_x86_elf_adjust_dynamic_symbol): New.
	(elf_backend_adjust_dynamic_symbol): Likewise.