init: load ttyterm by default, winman can be run from there if the system is set up for graphical use.
posix: in devfs, updated RandomFile to use rand(), and FramebufferFile to expose commands defined in sys/fb.h
apps: update winman and ttyterm to use sys/fb.h protocol for setting graphics mode.
posix: call File::command and File::supports in posix_ioctl.
posix: FramebufferFile now sets the file size when it sets a new graphics mode.