[AArch64] Optimize .gnu.hash table size for executable

bfd/
	* elfnn-aarch64.c (elf_aarch64_hash_symbol): New function.
	(elf_backend_hash_symbol): Define.

ld/
	* testsuite/ld-aarch64/aarch64-elf.exp (aarch64elflinktests): New tests.
	* testsuite/ld-aarch64/func-in-so.s: New test source file.
	* testsuite/ld-aarch64/func-sym-hash-opt.s: Likewise.
	* testsuite/ld-aarch64/func-sym-hash-opt.d: New expected test result.
7 files changed