[gold patch] Fix internal error with --start-lib and object file with no global syms

[Cary Coutant]

>>         * archive.cc (Lib_group::add_symbols): Lock object before deleting its
>>         symbols data.
>>         (Lib_group::include_member): Unlock object after deleting its
>>         symbols data.
>>         * testsuite/start_lib_test_3.c: Remove all global symbols to trigger
>>         the bug fixed here.

> Remove space before left parenthesis in gold_assert line.
>
> This is OK with that change.

Thanks, committed.

-cary