Pass USB CV test verification;
Code cleanup;

Some driver will emit USB_MSG_DATA_NOTIFY before the USB get configured.
Filter out those events.

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.

When the USB got RESET packet from the host and the address is setup,
all the classes will got reset. The reset is done by class stop and than
class run. So the classes should reset their internal state in
class_{run,stop}.

Besides, the USB device driver could post a USB_MSG_RESET message on
every RESET packet.

Although currently the only message send to the queue is struct
udev_msg, in order to keep backward compacity and for extention in the
future, we set the size of message to 32.

It also add two configurations for the USB device even loop thread:

    RT_USBD_THREAD_STACK_SZ to set the stack size, default to 2048
    RT_USBD_THREAD_PRIO     to set the priority, default to 8

You can overwrite the default values in rtconfig.h

Sort the switch cases by the frequency of the events.

This could crash the program with -O1 and -O2 in MDK.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2579 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2563 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2500 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2490 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2480 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2477 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2447 bbd45198-f89e-11dd-88c7-29a3b14d5316

& modify some comment in rt_usb_device_init

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2346 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2344 bbd45198-f89e-11dd-88c7-29a3b14d5316

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2332 bbd45198-f89e-11dd-88c7-29a3b14d5316