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

 Index: gcc-4.2/gcc/Makefile.in

 ===================================================================

 --- gcc-4.2/gcc/Makefile.in	(revision 121758)

 +++ gcc-4.2/gcc/Makefile.in	(working copy)

 @@ -2658,7 +2658,7 @@ mips-tdump.o : mips-tdump.c $(CONFIG_H) 

  # FIXME: writing proper dependencies for this is a *LOT* of work.

  libbackend.o : $(OBJS-common:.o=.c) $(out_file) \

    insn-config.h insn-flags.h insn-codes.h insn-constants.h \

 -  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE)

 +  insn-attr.h  $(DATESTAMP) $(BASEVER) $(DEVPHASE) gcov-iov.h

  	$(CC) $(ALL_CFLAGS) $(ALL_CPPFLAGS) \

  	  -DTARGET_NAME=\"$(target_noncanonical)\" \

  	  -DLOCALEDIR=\"$(localedir)\" \