gold patch for fixing ICF bugs.

[Cary Coutant]

>        * icf.cc (get_section_contents): Check for preemptible functions.
>        Ignore addend when appropriate.
>        * symtab.cc (should_add_dynsym_entry): Add new parameter.  Check for
>        section folded.
>        (add_from_relobj): Check for section folded.
>        (set_dynsym_indexes): Fix call to should_add_dynsym_entry.
>        * symtab.h (should_add_dynsym_entry): Add new parameter.
>        * target-reloc.h (scan_relocs): Check for section folded.
>        * x86_64.cc (Target_x86_64::Scan::possible_function_pointer_reloc):
>        Check reloc types for function pointers in shared objects.
>        * testsuite/Makefile.am (icf_virtual_function_folding_test): New test
>        case.
>        (icf_preemptible_functions_test): New test case.
>        (icf_string_merge_test): New test case.
>        * testsuite.Makefile.in: Regenerate.
>        * testsuite/icf_safe_so_test.sh: Change to not fold foo_glob and
>        bar_glob.  Refactor code.
>        * testsuite/icf_preemptible_functions_test.cc: New file.
>        * testsuite/icf_preemptible_functions_test.sh: New file.
>        * testsuite/icf_string_merge_test.cc: New file.
>        * testsuite/icf_string_merge_test.sh: New file.
>        * testsuite/icf_virtual_function_folding_test.cc: New file.
>        * testsuite/icf_virtual_function_folding_test.sh: New file.

It looks good to me; I just have a nit on one comment:

+		  long long offset = it_a->first;
+
+                  unsigned long long addend = it_a->second;
+                  // Ignoring the addend when it is a negative value --
+                  // this is taken from function 'Value' in file 'object.h'.
+                  if (addend < 0xffffff00)
+                    offset = offset + it_a->second;

The comment should be a complete sentence: "Ignore the addend when
...". Instead of saying "this is taken from", it would be better to
say "See the comments for Merged_symbol_value::value() in object.h."

-cary