Add gdbarch_in_function_epilogue_p hook for sparc64.

Add gdbarch_in_function_epilogue_p hook for sparc64.

watchpoint_update and watchpoint_cond avoid checking for
watchpoints when we are located at a function epilogue in the
current frame.  This is done in order to avoid using corrupted
local registers and unwinding a corrupted/destroyed stack.

The code determining whether we are in a function epilogue is
provided by the backends via the gdbarch_in_function_epilogue_p
hook.  This commit adds such a hook for sparc64 targets.

2014-02-10  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* sparc-tdep.c (sparc_in_function_epilogue_p): New function.
	(X_RETTURN): New macro.
	* sparc-tdep.h: sparc_in_function_epilogue_p prototype.

	* sparc64-tdep.c (sparc64_init_abi): Hook
	sparc_in_function_epilogue_p.