Add new CDC descriptor structs to the CDC class driver, so that the CDC demos can use human readable field names.
Rename prefix for Still Image Host class driver functions from "SImage_" to "SI_" to remain consistent with the rest of the driver.
Added brace guards to macros with parameters to prevent unintended changed evaluation of the macro expression.
Minor code cleanups (remove redundant comments, fix spacing, etc.).
Make all audio device Class Driver functions require a reference to the Audio class instance, so that the endpoint size can be checked (and to standardize the APIs).
Make LEDs more responsive in the AudioOutput device demos.
Added parameter directions to function parameter documentation.
Added new experimental FAST_STREAM_FUNCTIONS compile time option to speed up stream transfers at the expense of a higher FLASH consumption (needs testing to verify improved throughput).