Add stack alignment support to RTOS awareness - needed for ARM ABI processors

Change-Id: I69a2f3d0606a97d48b7738561a85da87f458b82b
Signed-off-by: Evan Hunter <ehunter@broadcom.com>
Reviewed-on: http://openocd.zylin.com/238
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Mathias Küster <kesmtp@freenet.de>
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>

src/rtos/rtos.h

@@ -91,6 +91,7 @@ struct rtos_register_stacking
 	unsigned char                       stack_registers_size;
 	signed   char                       stack_growth_direction;
 	unsigned char                       num_output_registers;
+	unsigned char                       stack_alignment;
 	const struct stack_register_offset* register_offsets;
 };