gdb/

	* aarch64-linux-nat.c (aarch64_linux_set_debug_regs): Set
	iov.iov_len with the real length in use.

gdb/gdbserver/

	* linux-aarch64-low.c (aarch64_linux_set_debug_regs): Set
	iov.iov_len with the real length in use.
gas/

	* config/tc-aarch64.c (md_assemble): Defer the feature checking until
	do_encode () succeeds.

gas/testsuite/

	* gas/aarch64/rm-simd-ext.d: New file.
	* gas/aarch64/rm-simd-ext.l: Likewise.
	* gas/aarch64/rm-simd-ext.s: Likewise.