NPTL is no longer an add-on!

sysdeps/unix/sysv/linux/configure

@@ -158,33 +158,6 @@ if test -n "$sysheaders"; then
   CPPFLAGS=$OLD_CPPFLAGS
 fi
 
-# Under Linux the NPTL add-on should be available.
-case $add_ons in
-  # It is available.  Good.
-  *nptl*)
-    nptl_missing=
-    ;;
-  *)
-    nptl_missing=yes
-    ;;
-esac
-
-if test "$nptl_missing"; then
-  if test $enable_sanity = yes; then
-    echo "\
-*** On GNU/Linux systems it is normal to compile GNU libc with the
-*** \`nptl' add-on.  Without that, the library will be
-*** incompatible with normal GNU/Linux systems.
-*** If you really mean to not use this add-on, run configure again
-*** using the extra parameter \`--disable-sanity-checks'."
-    exit 1
-  else
-    echo "\
-*** WARNING: Are you sure you do not want to use the \`nptl'
-*** add-on?"
-  fi
-fi
-
 if test "$prefix" = "/usr/local" -o "$prefix" = "/usr/local/" -o "$prefix" = "NONE"; then
   if test $enable_sanity = yes; then
     echo "\