* icf.cc (Icf::find_identical_sections): Unfold symbols that have
been maked as --keep-unique.
(Icf::unfold_section): New function.
* icf.h (Icf::unfold_section): New function.
* options.h (General_options::keep_unique): New option.
* testsuite/Makefile.am: Add commands to build icf_keep_unique_test.
* testsuite/Makefile.in: Regenerate.
* testsuite/icf_keep_unique_test.sh: New file.
* testsuite/icf_keep_unique_test.cc: New file.
