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

 diff -durN glibc-2.13.orig/elf/dl-lookup.c glibc-2.13/elf/dl-lookup.c

 --- glibc-2.13.orig/elf/dl-lookup.c	2009-03-30 23:14:32.000000000 +0200

 +++ glibc-2.13/elf/dl-lookup.c	2009-11-13 00:51:36.000000000 +0100

 @@ -301,6 +301,12 @@

  	      /* FALLTHROUGH */

  	    case STB_GLOBAL:

 	    success:

 +#ifdef __mips__

 +	      /* HACK: MIPS marks its lazy evaluation stubs with SHN_UNDEF

 +		 symbols, we skip them. */

 +	      if (sym->st_shndx == SHN_UNDEF)

 +		break;

 +#endif

  	      /* Global definition.  Just what we need.  */

  	      result->s = sym;

  	      result->m = (struct link_map *) map;