Reorder more powerpc64 sections for -z relro

Reorder more powerpc64 sections for -z relro

This moves .got too, which requires .sdata and .sbss to move with it,
because these sections share addressing via the toc pointer and with
small-model code must be within a 16-bit signed offset.  .plt, .iplt
and .branch_lt must also be moved since they are addressed via a
32-bit offset from the toc pointer, and we might have a very large
.data section.

This change means we may have some bss style sections before the data
segment, necessitating another PT_LOAD header.  Also, since _edata is
defined at the end of the data segment it's possible with an empty
.data to have _edata at the end of .plt which looks a little unusual
since .plt is a bss style section.  That should only happen rarely in
real world binaries, but does occur in the ld testsuite.

ld/
	* emulparams/elf64ppc.sh (BSS_PLT): Don't define.
	(OTHER_READWRITE_SECTIONS): Move .branch_lt to..
	(OTHER_RELRO_SECTIONS_2): ..here.
	(DATA_GOT, SEPARATE_GOTPLT, DATA_SDATA, DATA_PLT,
	PLT_BEFORE_GOT): Define.
	* scripttempl/elf.sc: Handle DATA_SDATA and DATA_GOT/DATA_PLT/
	PLT_BEFORE_GOT combination.
	(DATA_GOT, SDATA_GOT): Don't define if either is already defined.
ld/testsuite/
	* ld-powerpc/ambiguousv1.d,
	* ld-powerpc/ambiguousv1b.d,
	* ld-powerpc/ambiguousv2.d,
	* ld-powerpc/ambiguousv2b.d,
	* ld-powerpc/elfv2exe.d,
	* ld-powerpc/elfv2so.d,
	* ld-powerpc/tlsexe.r,
	* ld-powerpc/tlsexetoc.r,
	* ld-powerpc/tlsso.r,
	* ld-powerpc/tlstocso.r: Update.