ACM driver of USB Communication Device Class

Starting with this release, the usbsacm driver supports USB modems that conform to the Universal Serial Bus Communication Device Class Abstract Control Model (USB CDC ACM) specification. Customers can attach the usbsacm driver with their mobile phones, PCMCIA cards, or any modem-like devices. The usbsacm driver outputs term nodes under /dev/term/. Customers can then use pppd(1M) to transmit datagrams over these serial ports.