* config/avr/avr-protos.h (expand_epilogue): Change prototype
	* config/avr/avr.h (struct machine_function): Add field sibcall_fails.
	* config/avr/avr.c (init_cumulative_args)
	(avr_function_arg_advance): Use it.
	* config/avr/avr.c (expand_epilogue): Add bool parameter. Handle
	sibcall epilogues.
	(TARGET_FUNCTION_OK_FOR_SIBCALL): Define to...
	(avr_function_ok_for_sibcall): ...this new function.
	(avr_lookup_function_attribute1): New static Function.
	(avr_naked_function_p, interrupt_function_p)
	(signal_function_p, avr_OS_task_function_p)
	(avr_OS_main_function_p): Use it.
	* config/avr/avr.md ("sibcall", "sibcall_value")
	("sibcall_epilogue"): New expander.
	("*call_insn", "*call_value_insn"): New insn.
	("call_insn", "call_value_insn"): Remove
	("call", "call_value", "epilogue"): Change expander to handle
	sibling calls.

From-SVN: r171300