minor; clocking changes to stm32l4 nucleo to support CLK48 for  RNG functionality (and any others)

All configurations with CONFIG_PL2303 should also set CONFIG_LIB_BOARDCTL and CONFIG_BOARDCTL_USBDEVCTRL

basic support of STM32L4VG Discovery board.  Functioning nsh, leds, buttons.  Also compatible with, but not requiring, RNG code in 'arch'.

basic support of STM32L4VG Discovery board.  Functioning nsh, leds, buttons.  Also compatible with, but not requiring, RNG code in 'arch'.

Add configuration files that have CONFIG_CDCACM=y (and not CONFIG_CDCACM_COMPOSITE) must have CONFIG_LIB_BOARDCTL=y and CONFIG_BOARD_USBDEVCTRL=y

Add configuration files that have CONFIG_USBMSC=y (and not CONFIG_USBDEV_COMPOSITE) must have CONFIG_LIB_BOARDCTL=y and CONFIG_BOARD_USBDEVCTRL=y

All configurations that set CONFIG_SYSTEM_COMPOSITE must also select CONFIG_LIB_BOARDCTL and CONFIG_BOARDCTL_USBDEVCTL

Remove most unused references to CONFIG_NET_MULTICAST.  Rename other uses of CONFIG_NET_MULTICAST to avoid naming comflicts.