Add an AArch64 simulator to GDB.

Add an AArch64 simulator to GDB.

sim	* configure.tgt: Add aarch64 entry.
	* configure: Regenerate.
	* sim/aarch64/configure.ac: New configure template.
	* sim/aarch64/aclocal.m4: Generate.
	* sim/aarch64/config.in: Generate.
	* sim/aarch64/configure: Generate.
	* sim/aarch64/cpustate.c: New file - functions for accessing
	AArch64 registers.
	* sim/aarch64/cpustate.h: New header.
	* sim/aarch64/decode.h: New header.
	* sim/aarch64/interp.c: New file - interface between GDB and
	simulator.
	* sim/aarch64/Makefile.in: New makefile template.
	* sim/aarch64/memory.c: New file - functions for simulating
	aarch64 memory accesses.
	* sim/aarch64/memory.h: New header.
	* sim/aarch64/sim-main.h: New header.
	* sim/aarch64/simulator.c: New file - aarch64 simulator
	functions.
	* sim/aarch64/simulator.h: New header.

include/gdb * sim-aarch64.h: New file.

sim/test * configure: Regenerate.
	* sim/aarch64: New directory.