MFC r305130: Update to ELF Tool Chain r3490

Improvements include:
* readelf: report all relocation types in rel/rela for MIPS N64
* readelf: add ELFOSABI_ARM_AEABI
* elfdump: add ELFOSABI_ARM_AEABI and ELFOSABI_ARM
* Add recent RISC-V relocations
* elfcopy: use elftc_timestamp, to support SOURCE_DATE_EPOCH

MFC r305155: readelf: silence GCC 4.2.1 uninitialized variable warning

Sponsored by: The FreeBSD Foundation