* elflink.c (elf_link_input_bfd): Provide a file symbol for
each input file with local syms, if the input lacks such.
(bfd_elf_final_link): Add a file symbol to mark end of locals
for which we can associate with input files.
(struct elf_final_link_info): Add filesym_count field.
(struct elf_outext_info): Add need_second_pass and second_pass.
(elf_link_output_extsym): Detect symbols defined in the output
file, emit them on second pass over locals.
ld/testsuite/
Update to suit added STT_FILE symbols.
newly cloned section.
* ld-x86-64/split-by-file.rd: New test.
* ld-x86-64/split-by-file1.s: New test source code.
* ld-x86-64/split-by-file2.s: New test source code.
* ld-x86-64/x86-64.exp: Run the new test.
* readelf.c (process_section_headers): Mention meaning of 'l'
section flag for x86-64 targets.
