x86: Restore PC16 relocation overflow check

x86: Restore PC16 relocation overflow check

The x86-64 psABI has

---
A program or object file using R_X86_64_8, R_X86_64_16, R_X86_64_PC16
or R_X86_64_PC8 relocations is not conformant to this ABI, these
relocations are only added for documentation purposes.
---

Since x86 PC16 relocations have been used for 16-bit programs in an ELF32
or ELF64 container, PC16 relocation should wrap-around in 16-bit address
space.  Revert

commit a7664973b24a242cd9ea17deb5eaf503065fc0bd
Author: Jan Beulich <jbeulich@suse.com>
Date:   Mon Apr 26 10:41:35 2021 +0200

    x86: correct overflow checking for 16-bit PC-relative relocs

and xfail the related tests.  Also revert

commit 50c95a739c91ae70cf8481936611aa1f5397a384
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed May 26 12:13:13 2021 -0700

    x86: Propery check PC16 reloc overflow in 16-bit mode instructions

while keeping PR ld/27905 tests for PC16 relocation in 16-bit programs.

bfd/

	PR ld/27905
	* elf32-i386.c: Don't include "libiberty.h".
	(elf_howto_table): Revert commits a7664973b24 and 50c95a739c9.
	(elf_i386_rtype_to_howto): Revert commit 50c95a739c9.
	(elf_i386_info_to_howto_rel): Likewise.
	(elf_i386_tls_transition): Likewise.
	(elf_i386_relocate_section): Likewise.
	* elf64-x86-64.c (x86_64_elf_howto_table): Revert commits
	a7664973b24 and 50c95a739c9.
	(elf_x86_64_rtype_to_howto): Revert commit 50c95a739c9.
	* elfxx-x86.c (_bfd_x86_elf_parse_gnu_properties): Likewise.
	* elfxx-x86.h (elf_x86_obj_tdata): Likewise.
	(elf_x86_has_code16): Likewise.

binutils/

	PR ld/27905
	* readelf.c (decode_x86_feature_2): Revert commit 50c95a739c9.

gas/

	PR ld/27905
	* config/tc-i386.c (set_code_flag): Revert commit 50c95a739c9.
	(set_16bit_gcc_code_flag): Likewise.
	(x86_cleanup): Likewise.
	* testsuite/gas/i386/code16-2.d: Updated.
	* testsuite/gas/i386/x86-64-code16-2.d: Likewise.

include/

	PR ld/27905
	* elf/common.h (GNU_PROPERTY_X86_FEATURE_2_CODE16): Removed.

ld/

	PR ld/27905
	* testsuite/ld-i386/pcrel16-2.d: xfail.
	* testsuite/ld-x86-64/pcrel16-2.d: Likewise.