* collect2.c (DO_COLLECT_EXPORT_LIST): New internal macro,
        always defined.  Reflect definition or absence of such for
        COLLECT_EXPORT_LIST.  Readability helper.
        (scanfilter): New enum, to help control what symbols
        are to be considered or ignored by scan_prog_file.
        (enum pass): Rename as "scanpass", moved together with scanfilter
        prior to scan_prog_file's prototype.
        (scan_prog_file): Accept and honor scanpass and scanfilter arguments.
        Group prototype with the scanpass/scanfilter definitions, factorize
        head comments for the several implementations at the prototype.
        (main): Reorganize the first pass link control to let AIX
        drag only the needed frame tables in executables.  Prevent
        frame tables collection during the scan aimed at static ctors.
        Pre-link and scan for frame tables later to compensate.
        * doc/tm.texi (ASM_OUTPUT_DWARF_TABLE_REF): New macro.
        A C statement to issue assembly directives that create a reference
        to the given DWARF table identifier label from the current function
        section.
        * dwarf2out.c (switch_to_eh_frame_section): Add a BACK argument
        to differentiate first time section entry.  Only emit a .data
        tables start identifier label the first time around.
        (switch_to_frame_table_section): New function.  Helper for
        output_call_frame_info to switch possibly BACK into the eh_frame
        or the debug_frame section depending on FOR_EH.
        (output_call_frame_info): Use helper to first enter the proper
        frame section.
        (output_fde): Use ASM_OUTPUT_DWARF_TABLE_REF when defined to
        emit a link to the frame table start label from each function
        section.
        * config/rs6000/rs6000.c (rs6000_aix_asm_output_dwarf_table_ref):
        New function.  Implementation of ASM_OUTPUT_DWARF_TABLE_REF.
        * config/rs6000/rs6000-protos.h: Declare it.
        * config/rs6000/aix.h (ASM_OUTPUT_DWARF_TABLE_REF): Define.

From-SVN: r151157