Pass noaliases_p to aarch64_decode_insn

Pass noaliases_p to aarch64_decode_insn

Nowadays aarch64_decode_insn is a public interface used by both
opcodes and gdb.  However, its behaviour relies on a global variable
no_aliases, which isn't a good practise.  On the other hand, In default,
no_aliases is zero, but in GDB, we do want no alias when decoding
instructions for prologue analysis (patches to be posted), so that we
can handle both instructions "add" and "mov" (an alias of "add") as
"add".  The code in GDB can be simplified.

This patch adds a new argument in aarch64_decode_insn, and pass no_aliases
to it.  In GDB side, always pass 1 to it.

include/opcode:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64.h (aarch64_decode_insn): Update declaration.

opcodes:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64-dis.c	(aarch64_decode_insn): Add one argument
	noaliases_p.  Update comments.  Pass noaliases_p rather than
	no_aliases to aarch64_opcode_decode.
	(print_insn_aarch64_word): Pass no_aliases to
	aarch64_decode_insn.

gdb:

2015-10-28  Yao Qi  <yao.qi@linaro.org>

	* aarch64-tdep.c (aarch64_software_single_step): Pass 1 to
	aarch64_decode_insn.