Various SAM4S related fixes, mostely related to the timer driver driver and the SAM4S timer/counter.  All from Bob Doisin

LPC17xx:  Prioritized interrupts are not supported (although hooks are present to prioritize interrupts).  Make LPC17 Ethernet default priority to be the system default, not the highest.  If the unsupported feature is enabled, then at least it should do no harm

LPC17xx, TIVA, and Kinetis interrupt initialization:  use the NVIC ICTR register to determine how many interrupt lines/registers are supported by the MCU