bsd.h (ASM_FILE_START): Don't use dump_base_name...
* i386/bsd.h (ASM_FILE_START): Don't use dump_base_name, it is
wrong and should only be used for dump related things, not
debugging information, instead main_input_filename should be used.
Also, reuse output_file_directive if possible.
* i386/aix386ng.h (ASM_FILE_START): Likewise.
* i386/isc.h (ASM_FILE_START): Likewise.
* i386/win-nt.h (ASM_FILE_START): Likewise.
* i386/sun386.h (ASM_FILE_START): Likewise.