* final.c (debug_flush_symbol_queue): New function.
        (debug_queue_symbol): New function.
        (debug_free_queue): New function.
        (debug_nesting): New variable.
        (symbol_queue): New variable.
        (symbol_queue_index): Same.
        (symbol_queue_size): Same.
        * debug.h (debug_flush_symbol_queue): New.
        (debug_queue_symbol): New.
        (debug_free_queue): New.
        (debug_nesting): New.
        (symbol_queue_index): New.
        * dbxout.c (DBXOUT_DECR_NESTING): New macro.
        (DBXOUT_DECR_NESTING_AND_RETURN): New macro.
        (dbxout_init): Delay symbol output.
        (dbxout_global_decl): Save, set and reset TREE_USED bit around dbxout_symbol()
        call.
        (dbxout_begin_function): Same.
        (dbxout_finish): Free symbol queue.
        (dbxout_type): Put appropriate symbols in queue.
        (dbxout_symbol): Put info for symbol's type in queue. Decrement/Increment
        nesting counts flush symbol queue appropriately.
        (dbxout_parms): Increment dbxout nesting.
        (dbxout_reg_parms): Same.
        * flags.h (flag_debug_only_used_symbols): New.
        * toplev.c (flag_debug_only_used_symbols): New variable.
        (lang_independent_options): Add entries for new option -feliminate-unused-debug-symbols.
        * common.opt: Add entry for -feliminate-unused-debug-symbols.
        * opts.c (common_handle_options): Same.
        * config/rs6000/darwin.h (CC1_SPEC): Interpret -gused as -feliminate-unused-debug-symbols.
        * doc/invoke.texi (Debugging Options): Document -feliminate-unused-debug-symbols.

From-SVN: r68556