arch/powerpc: add powerpc64le support

Technically, I don't forbid powerpcle support either, but I'm not sure that
there is any library/compiler support for that at the moment (though the hw
technically makes it possible).

powerpc64le needs glibc 2.19 and gcc 4.9. I haven't looked into the support
tools, but at least gdb 7.5 is too old (7.7.1 definitely has support).

Also make powerpc64 non-experimental. It's practically old at this point.

Signed-off-by: Cody P Schafer <dev@codyps.com>
[yann.morin.1998@free.fr: use ${target_endian_le} and ${target_bits_64}]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <64bfbbced9dd8f62e0d6.1399801945@gun>
Patchwork-Id: 347775

 alpha does not have a __NR_creat

 http://bugs.gentoo.org/227275

 http://sourceware.org/bugzilla/show_bug.cgi?id=6650

 diff -durN glibc-2.13.orig/sysdeps/unix/sysv/linux/wordsize-64/creat64.c glibc-2.13/sysdeps/unix/sysv/linux/wordsize-64/creat64.c

 --- glibc-2.13.orig/sysdeps/unix/sysv/linux/wordsize-64/creat64.c	2007-11-10 20:34:26.000000000 +0100

 +++ glibc-2.13/sysdeps/unix/sysv/linux/wordsize-64/creat64.c	2009-11-13 00:50:51.000000000 +0100

 @@ -1 +1,5 @@

  /* Defined as alias for the syscall.  */

 +#include <sysdep.h>

 +#ifndef __NR_creat

 +#include "../../../../../io/creat64.c"

 +#endif