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

Original patch from H.J. Lu, as reported there:

http://www.nabble.com/PATCH:-Use-short-for-fnstsw-td14775171.html

fnstsw stores 16bit into %ax. The upper 16bit of %eax is unchanged.

The new assembler (binutils-2.18.50.0.4 and up) will disallow "fnstsw %eax".

diff -dur glibc-2.7.orig/sysdeps/i386/fpu/ftestexcept.c glibc-2.7/sysdeps/i386/fpu/ftestexcept.c

--- glibc-2.7.orig/sysdeps/i386/fpu/ftestexcept.c	2004-03-05 11:14:48.000000000 +0100

+++ glibc-2.7/sysdeps/i386/fpu/ftestexcept.c	2008-06-24 10:54:43.000000000 +0200

@@ -26,7 +26,7 @@

 int

 fetestexcept (int excepts)

 {

-  int temp;

+  short temp;

   int xtemp = 0;

   /* Get current exceptions.  */