Added little utitlity to decode control request types.

The utility decode-request-type will print the value of the direction,
type and recipient fields from a request type value.

Example:

$ ./decode-ctrl-transfer 161
direction=in, type=class, recipient=interface

$ ./decode-ctrl-transfer 0x35
direction=out, type=class, recipient=reserved

$ ./decode-ctrl-transfer 0b10000000
direction=in, type=standard, recipient=device