usb: add USB_MSG_PLUG_OUT event

When the core received an USB_MSG_PLUG_OUT event, it will stop all the
classes. This make a chance that the classes could get rid off doing
useless stuff while the USB cable is plugged out.
usbdevice/core: cope with some buggy drivers on USB_MSG_DATA_NOTIFY

Some driver will emit USB_MSG_DATA_NOTIFY before the USB get configured.
Filter out those events.
Merge pull request #100 from grissiom/usb-plug

usb: add USB_MSG_PLUG_OUT event
udisk can be eject
Merge pull request #103 from heyuanjie87/ForPullRequest

udisk can be ejected
ident format

Signed-off-by: visitor83 <root@wolflouis.(none)>
Merge pull request #104 from visitor83/gdb

indent format cortex-m3/cpuport.c, thank peter.uboot@gmail.com