scripts: do not provide to-sysroot include symlink

Do not provide the PREFIX/TUPLE/include -> SYSROOT/usr/include symlink,
and let gcc install its dependable C++ headers were it sees fit to
install them.

See the test by Anthony (by the end of the messages):
http://sourceware.org/ml/crossgcc/2010-10/msg00129.html
http://sourceware.org/ml/crossgcc/2010-10/msg00134.html

See also the comment by Arnaud:
http://sourceware.org/ml/crossgcc/2010-10/msg00157.html

Reported-by: Anthony Foiani <anthony.foiani@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 --- glibc-2.6.1/sysdeps/unix/sysv/linux/kernel-features.h	2006-07-29 07:43:27.000000000 +0300

 +++ glibc-2.6.1/sysdeps/unix/sysv/linux/kernel-features.h.new	2008-07-26 08:45:06.000000000 +0300

 @@ -445,7 +445,7 @@

  /* The *at syscalls were introduced just after 2.6.16-rc1.  Due to the way the

     kernel versions are advertised we can only rely on 2.6.17 to have

     the code.  */

 -#if __LINUX_KERNEL_VERSION >= 0x020611

 +#if __LINUX_KERNEL_VERSION >= 0x020611 && !defined __alpha__

  # define __ASSUME_ATFCTS	1

  #endif