Add -z noextern-protected-data to ld for ELF/x86

Add -z noextern-protected-data to ld for ELF/x86

Address of protected data defined in the shared library may be external,
i.e., due to copy relocation.  By default, linker backend checks if
relocations against protected data symbols are valid for building shared
library and issues an error if relocation isn't allowed.  The new option
override linker backend default.  When -z noextern-protected-data is used,
updates on protected data symbols by another module won't be visibile
to the resulting shared library.  This option is specific to ELF/i386
and ELF/x86-64.

bfd/

	PR ld/pr17709
	* elflink.c (_bfd_elf_adjust_dynamic_copy): Check
	info->extern_protected_data when warning copy relocs against
	protected symbols.
	(_bfd_elf_symbol_refs_local_p): Check info->extern_protected_data
	when checking protected non-function symbols.

include/

	PR ld/pr17709
	* bfdlink.h (bfd_link_info): Add extern_protected_data.

ld/

	PR ld/pr17709
	* ld.texinfo: Document "-z noextern-protected-data".
	* ldmain.c (main): Initialize link_info.extern_protected_data
	to -1.
	* lexsup.c (elf_shlib_list_options): Add
	"-z [no]extern-protected-data".
	* emulparams/elf32_x86_64.sh: Source extern_protected_data.sh.
	* emulparams/elf_i386.sh: Likewise.
	* emulparams/elf_i386_be.sh: Likewise.
	* emulparams/elf_i386_chaos.sh: Likewise.
	* emulparams/elf_i386_ldso.sh: Likewise.
	* emulparams/elf_i386_vxworks.sh: Likewise.
	* emulparams/elf_k1om.sh: Likewise.
	* emulparams/elf_l1om.sh: Likewise.
	* emulparams/elf_x86_64.sh: Source extern_protected_data.sh.
	(PARSE_AND_LIST_OPTIONS): Renamed to ...
	(PARSE_AND_LIST_OPTIONS_BNDPLT): This.
	(PARSE_AND_LIST_ARGS_CASE_Z): Renamed to ...
	(PARSE_AND_LIST_ARGS_CASE_Z_BNDPLT): This.
	(PARSE_AND_LIST_OPTIONS): Append $PARSE_AND_LIST_OPTIONS_BNDPLT.
	(PARSE_AND_LIST_ARGS_CASE_Z): Append
	$PARSE_AND_LIST_ARGS_CASE_Z_BNDPLT.
	* emulparams/extern_protected_data.sh: New file.

ld/testsuite/

	PR ld/pr17709
	* ld-i386/i386.exp: Run protected6b.
	* ld-i386/protected6b.d: New file.
	* ld-x86-64/protected6b.d: Likewise.
	* ld-x86-64/x86-64.exp:  Run protected6b.