* dlltool.c (add_stdcall_underscore): New flag.
(xlate): Also add underscore to stdcall symbol if
add_stdcall_underscore set.
(usage): Document --add-stdcall-underscore option.
(OPTION_ADD_STDCALL_UNDERSCORE): New define.
(long_options): Use it for --add-stdcall-underscore option.
(main): Handle it.
* doc/binutils.texi: Document --add-stdcall-underscore option
and differentiate from --add-underscore.