patch / RFD: speed up linker map file generation

[Nick Clifton]

Hi Joern,

> I have merged my patch into the mainline from Sunday and implemented your
> suggestions.

Great - there a few more minor things that need fixing:

   * The new switch should be documented in ld.texinfo.  This entry also 
ought to mention that it may enable other tweaks to the linker's 
behaviour in the future.

   * A new feature like this should be mentioned in the ld/NEWS file as 
well.

   * You are still adding two extra fields to user_section_struct, even 
if --reduce-memory-overheads is enabled.  It would be better I think if 
you had two different structures, one with the extra fields, and then 
altered the get_userdata() macro and the init_os() function to select 
the right one depending upon the command line switch.

Cheers
   Nick