ld/x86: Add -z report-relative-reloc

Linker generated relative relocations don't have symbol info:

[hjl@gnu-cfl-2 tmpdir]$ readelf -rW dump

Relocation section '.rela.dyn' at offset 0x180 contains 2 entries:
 Offset     Info    Type                Sym. Value  Symbol's Name + Addend
00002f70  00000008 R_X86_64_RELATIVE                 1000
00002f68  00000025 R_X86_64_IRELATIVE                1007
[hjl@gnu-cfl-2 tmpdir]$

Add -z report-relative-reloc to x86 ELF linker to report dynamic relative
relocations:

[hjl@gnu-cfl-2 tmpdir]$ ../ld-new -pie -melf32_x86_64 -z report-relative-reloc -o dump report-reloc-1.o
dump: R_X86_64_IRELATIVE (offset: 0x00002f68, info: 0x00000025, addend: 0x00001007) against 'ifunc' for section '.data.rel.ro.local' in report-reloc-1.o
dump: R_X86_64_RELATIVE (offset: 0x00002f70, info: 0x00000008, addend: 0x00001000) against '_start' for section '.data.rel.ro.local' in report-reloc-1.o
[hjl@gnu-cfl-2 tmpdir]$

It can be used to map relative relocations to corresponding symbols.

bfd/

	* elf-linker-x86.h (elf_linker_x86_params): Add
	report_relative_reloc.
	* elf32-i386.c (elf_i386_relocate_section): Call
	_bfd_x86_elf_link_report_relative_reloc to report relative
	relocations for -z report-relative-reloc.
	(elf_i386_finish_dynamic_symbol): Likewse.
	* elf64-x86-64.c (elf_x86_64_relocate_section): Likewse.
	(elf_x86_64_finish_dynamic_symbol): Likewse.
	* elfxx-x86.c (_bfd_x86_elf_link_report_relative_reloc): New
	function.
	* elfxx-x86.h (_bfd_x86_elf_link_report_relative_reloc): New
	prototype.

ld/

	* NEWS: Mention -z report-relative-reloc.
	* ld.texi: Document -z report-relative-reloc.
	* emulparams/elf32_x86_64.sh: Source x86-report-relative.sh.
	* emulparams/elf_i386.sh: Likewse.
	* emulparams/elf_x86_64.sh: Likewse.
	* emulparams/x86-report-relative.sh: New file.
	* testsuite/ld-i386/report-reloc-1.d: Likewse.
	* testsuite/ld-i386/report-reloc-1.l: Likewse.
	* testsuite/ld-i386/report-reloc-1.s: Likewse.
	* testsuite/ld-x86-64/report-reloc-1-x32.d: Likewse.
	* testsuite/ld-x86-64/report-reloc-1.d: Likewse.
	* testsuite/ld-x86-64/report-reloc-1.l: Likewse.
	* testsuite/ld-x86-64/report-reloc-1.s: Likewse.
	* testsuite/ld-i386/i386.exp: Run report-reloc-1.
	* testsuite/ld-x86-64/x86-64.exp: Run report-reloc-1 and
	report-reloc-1-x32.