bug#21098: uname man page

[Paul Eggert]

Thanks, that patch looks good, except for some nits.  POSIX spells the phrase 
"non-portable" and we might as well be consistent.  The --help lines would look 
better as:

  -p, --processor          print the processor type (non-portable)\n\
  -i, --hardware-platform  print the hardware platform (non-portable)\n\
as the period would look funny after a non-capitalized sentence.