Patch to not create GOT and dynamic relocation entries for unresolved symbols with --warn-unresolved-symbols.

[Cary Coutant]

        * options.h (--warn-unresolved-symbols): New option.

s/warn/weak/

        * symtab.cc (Symbol_table::sized_write_globals): Change symbol
        binding to weak with new option.
        * symtab.h (is_weak_undefined): Check for new option.
        (is_strong_undefined): Check for new option.
        * testsuite/Makefile.am(weak_unresolved_symbols_test): New test.
        * testsuite/Makefile.in: Regenerate.
        * testsuite/weak_unresolved_symbols_test.cc: New file.

This file is missing from the patch. (Don't forget to "git add".)

        * Makefile.in: Side-effect from running automake.

Since you didn't change Makefile, just remove this from the patch
("git checkout Makefile" after running automake). Otherwise, we'll
keep ping-ponging uselessly between the two (or more) variations that
automake generates.

+      // If --weak-unresolved-symbols is set, change binding of unresolved
+      // global symbols to STB_WEAK.
+      if (parameters->options().weak_unresolved_symbols()
+         && (binding == elfcpp::STB_GLOBAL
+             || binding == elfcpp::STB_LOCAL)

Why check for STB_LOCAL? Local symbols can't be unresolved. What about
STB_GNU_UNIQUE symbols? (Perhaps that's what you meant.)

-cary