Correct unitialization of composite USB device.  A stale pointer was being reused.  From David Sidrane

STM32 F1 USB device:  Fix handling of EP0 start for large buffers; Add support for decoded USB trace strings.  From Davice Sidrane

Avoid calling pthread_join() to wait for USB MSC thread to terminate:  This does not work if the caller of usb_mscuninitialize() is in a different task group than the MSC thread.  From David Sidrane

Extend stack debug logic to include IDLE and interrupt stacks.  Also color the heap as well.  Based on suggestions from David Sidrane

Add an MTD device wrapper that can used to provide a /dev/config that can be used for retaining configuration data.  From Ken Pettit

arch/arm/src/stm32/stm32_usbdev.c: On a failure to bind the class driver, the driver reference was being nullified too soon.  This caused an exception in usbdev_reset() later.  The driver reference will be null
ified later usbdev_unregister when the caller gets the error.  From David Sidrane