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>

source "config/backend.in"

source "config/global.in"

source "config/target.in"

source "config/toolchain.in"

source "config/kernel.in"

source "config/binutils.in"

source "config/cc.in"

source "config/libc.in"

source "config/debug.in"

source "config/companion_libs.in"

source "config/companion_tools.in"

source "config/test_suite.in"