Preserve all mapping symbols in ARM and AArch64 object files.
bfd * elfnn-aarch64.c (is_aarch64_mapping_symbol): New function. Returns TRUE for AArch64 mapping symbols. (elfNN_aarch64_backend_symbol_processing): New function. Marks mapping symbols as precious in object files so that they will not be stripped. (elf_backend_symbol_processing): Define. * elf32-arm.c (is_arm_mapping_symbol): New function. Returns TRUE for ARM mapping symbols. (elf32_arm_backend_symbol_processing): Make use of the new function.