52226b7 - Added basic flip2 support.
58964f7 - Added usb_control_code_t, control writes are now void.
dfc969d - Added string descriptors, control_read, control_write.
f21c618 - Added yb::utf16le_to_utf8.
5a43b65 - Implementation of task::then no longer rethrows.
0f8198c - Added send_avr232boot_escape_seq.
3d2da73 - Added task::cancellable and task::finishable.
2273fca - Fixed: tunnel_stream now completes read requests.
84d827e - Fixed: the destructor of usb_interface_guard is now nothrow.
9ac9cdc - Fixed a typo.