arch/arm/src/lpc54xx:  Fix some GPIO interrupt configuration errors.  Add logic to acknowledge rising/falling edge events.  config/lpcxpresso-lpc545628:  Add an intermediate interrupt handler to support acknowledgement of rising and falling edge interrupts.

arch/arm/src/lpc54xx:  Implement GPIO interrupt support.  configs/lpcxpress-lpc54628:  Add support for the USER button.  Enable the apps/examples/button test in the NSH configuration.

configs/lpcxpresso-lp54629: Add logic to configure EMC pins. arch/arm/src/lpc54xx: Correct GPIO read/write logic.  Update pin configuration for EMC pins.  All should have the input file offset and fast slew rate.

    configs/lpcxpresso-lpc54628:  Add support for on-board LEDs.
    arch/arm/src/lpc54xx:  Add support for GPIO/Peripheral pin configuration.
    arch/arm/src/lpc54xx/chip:  Add IOCON register definition file.
    arch/arm/src/lpc54xx:  Add GPIO and (incomplete) PINT register definition header files.