powerpc gold, work around pr17670

pr17670 is about an assert triggering on a branch to an undefined
weak symbol, the symbol being undefined due to dropping its comdat
group section.  (Well sort of.  The symbol is actually defined in
an .opd section which isn't part of the group, but the code section
the opd entry points at is dropped.)  So don't assert.
Also, don't make long branch stubs to such symbols, and arrange to
have target-reloc.h code warn when applying relocs that use the sym.

	PR 17670
	* symtab.cc (Symbol::set_undefined): Remove assertion.
	* powerpc.cc (Target_powerpc::symval_for_branch): Don't assert
	on symbols defined in discarded sections, instead return false.
	Rearrange params, update all callers.
	(Target_powerpc::Branch_info::make_stub): Don't make stubs for
	branches to syms in discarded sections.
	(Global_symbol_visitor_opd::operator()): Set discarded opd syms
	undefined and flag as discarded.
	(Target_powerpc::Relocate::relocate): Localize variable.
PowerPC gold, fix 32-bit branch address arithmetic

Mixing 64-bit and 32-bit types led to the wrong promotions.  Keep
calculation in same type.  Also fix a case where PLTREL24 reloc addend
should be ignored.

	* Powerpc.cc (Target_powerpc::Branch_info::make_stub): Ignore
	addend of PLTREL24 reloc when not generating a plt stub.  Make
	max_branch_offset an "Address".
	(Target_powerpc::Relocate::relocate): Make max_branch_offset
	an "Address".
Automatic date update in version.in
Add _bfd_elf_ifunc_get_synthetic_symtab

In i386 and x86-64 binaries with ifunc, relocations against .got.plt
section may not be in the same order as entries in PLT section.  This
patch adds _bfd_elf_ifunc_get_synthetic_symtab.  It takes a function
pointer which returns an array of PLT entry symbol values.  It calls
the function pointer to get the PLT entry symbol value array indexed
by relocation index, instead of calling plt_sym_val on each relocation
index.

	PR binutils/17677
	* elf-bfd.h (_bfd_elf_ifunc_get_synthetic_symtab): New prototype.
	* elf-ifunc.c (_bfd_elf_ifunc_get_synthetic_symtab): New
	function.
	* elf32-i386.c (elf_i386_plt_sym_val): Removed.
	(elf_backend_plt_sym_val): Likewise.
	(elf_i386_get_plt_sym_val): New.
	(elf_i386_get_synthetic_symtab): Likewise.
	(bfd_elf32_get_synthetic_symtab): Likewise.
	* elf64-x86-64.c (elf_x86_64_plt_sym_val): Removed.
	(elf_x86_64_plt_sym_val_offset_plt_bnd): Likewise.
	(elf_backend_plt_sym_val): Likewise.
	(elf_x86_64_get_plt_sym_val): New.
	(elf_x86_64_get_synthetic_symtab): Use
	_bfd_elf_ifunc_get_synthetic_symtab.
	(bfd_elf64_get_synthetic_symtab): Don't undefine for NaCl.