Add __VA_ARGS__ support to the LUFA supplied ISR macro. Add proper result typecasting to the SWAPENDIAN_* macros.

Switch to using -1 on the UC3 target to obtain a register mask with all bits set (for clearing interrupts and status flags).

Fix incorrect USB controller mode on the UC3 when a fixed mode is specified as a compile time option due to AVR32_USBB.USBCON.uide being set by default.

Make USB_Descriptor_String_t use a uint16_t for Unicode strings on all targets except the AVR8 (retained for backwards compatibility).