[LD, AArch64] Move ELF options behind -z

This patch moves the current AArch64 ld options of --force-bti
and --pac-plt to -z force-bti and -z pac-plt since these are
ELF specific options.

*** bfd/ChangeLog ***

2019-06-06  Sudakshina Das  <sudi.das@arm.com>

	* bfd-in.h: Change comment.
	* bfd-in2.h: Regenerate.
	* elfnn-aarch64.c (elfNN_aarch64_merge_gnu_properties): Update warning.
	* elfxx-aarch64.c (_bfd_aarch64_elf_link_setup_gnu_properties):
	Likwise.

*** ld/ChangeLog ***

2019-06-06  Sudakshina Das  <sudi.das@arm.com>

	* NEWS: Update options names.
	* emultempl/aarch64elf.em (OPTION_FORCE_BTI, OPTION_PAC_PLT): Remove.
	(PARSE_AND_LIST_LONGOPTS): Remove force-bti and pac-plt.
	(PARSE_AND_LIST_OPTIONS): Update to -z.
	(PARSE_AND_LIST_ARGS_CASE_Z_AARCH64): New.
	(PARSE_AND_LIST_ARGS_CASE_Z): Add PARSE_AND_LIST_ARGS_CASE_Z_AARCH64.
	(PARSE_AND_LIST_ARGS_CASES): Move cases for these options.
	* testsuite/ld-aarch64/bti-pac-plt-1.d: Update option.
	* testsuite/ld-aarch64/bti-pac-plt-2.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-1.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-2.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-3.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-4.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-6.d: Likewise.
	* testsuite/ld-aarch64/bti-plt-7.d: Likewise.
	* testsuite/ld-aarch64/bti-warn.d: Likewise.
	* testsuite/ld-aarch64/pac-plt-1.d: Likewise.
	* testsuite/ld-aarch64/pac-plt-2.d: Likewise.