aarch64: Enable ifunc support.

aarch64: Enable ifunc support.

Add support for handling the R_AARCH64_IRELATIVE relocation and
STT_GNU_IFUNC symbols to the aarch64 port.

ports/ChangeLog.aarch64:

2013-11-26  Will Newton  <will.newton@linaro.org>

	* sysdeps/aarch64/dl-irel.h: Include ldsodefs.h.
	(ELF_MACHINE_IRELA): Define.  (elf_ifunc_invoke): Pass
	hwcap to ifunc resolver function.  (elf_irela): New function.
	* sysdeps/aarch64/dl-machine.h: Include dl-irel.h.
	(elf_machine_rela) Handle STT_GNU_IFUNC symbols and
	R_AARCH64_IRELATIVE relocations.  (elf_machine_lazy_rel):
	Handle R_AARCH64_IRELATIVE relocations.