allows the user to custom PID and VID;
add a dcd operation to send status in control transfer
move the define related to Mass to mstorage.h
remove product ID
allows the user custom PID and VID
move the define related to Mass to here;
remove product ID
add lwip 1.4.1 source code
use new interface to send status in control transfer
allows the user custom PID and VID
revert the define
fix math.h

Declare sin/cos and M_PI in math.h.
Merge pull request #10 from grissiom/fix-math

fix math.h
Merge pull request #9 from heyuanjie87/usb-device

Usb-device
revert some define to usb_common.h
Correct macro definition
Merge pull request #12 from heyuanjie87/usb-device

Usb device:correct the macro