Updated makefiles to reflect new dfu-ee programming target invocations (supplied by Opendous, Inc.).

Renamed the ATTR_ALWAYSINLINE function attribute macro to ATTR_ALWAYS_INLINE to match the style of the other function attribute macro names.

Added ATTR_ALWAYS_INLINE attribute to several inlined library functions, to ensure they are inlined in all circumstances.

Cleanups to Endpoint.h and Pipe.h. Added better documentation for the endpoint and pipe interrupts.