Work on scs.h register and also nvic.h.

ARM Interrupt API (see nvic.h).
ARM SysTick API (see systick.h).
Example using both Interrupt and SysTick and blink LED1/2/3 see systickdemo.c.

lib/lpc43xx/Makefile

@@ -31,7 +31,7 @@ CFLAGS		= -O2 -g -Wall -Wextra -I../../include -fno-common \
 		  -mfloat-abi=hard -mfpu=fpv4-sp-d16
 # ARFLAGS	= rcsv
 ARFLAGS		= rcs
-OBJS		= gpio.o vector.o scu.o i2c.o ssp.o
+OBJS		= gpio.o vector.o scu.o i2c.o ssp.o nvic.o systick.o
 
 # VPATH += ../usb