Add descriptor class, subclass and protocol constants to the class drivers, modify all demos to use them where possible.

Move out private/internal host class driver constants to the common class driver headers, so that they can be used in the Low Level host mode demos.

Ensure all demos, projects and bootloaders use the class driver constants where possible to minimise code repetition.

Demos/Device/LowLevel/Mouse/Descriptors.c

@@ -83,9 +83,9 @@ USB_Descriptor_Device_t PROGMEM DeviceDescriptor =
 	.Header                 = {.Size = sizeof(USB_Descriptor_Device_t), .Type = DTYPE_Device},
 
 	.USBSpecification       = VERSION_BCD(01.10),
-	.Class                  = 0x00,
-	.SubClass               = 0x00,
-	.Protocol               = 0x00,
+	.Class                  = USB_CSCP_NoDeviceClass,
+	.SubClass               = USB_CSCP_NoDeviceSubclass,
+	.Protocol               = USB_CSCP_NoDeviceProtocol,
 
 	.Endpoint0Size          = FIXED_CONTROL_ENDPOINT_SIZE,
 
@@ -131,9 +131,9 @@ USB_Descriptor_Configuration_t PROGMEM ConfigurationDescriptor =
 
 			.TotalEndpoints         = 1,
 
-			.Class                  = 0x03,
-			.SubClass               = 0x01,
-			.Protocol               = 0x02,
+			.Class                  = HID_CSCP_HIDClass,
+			.SubClass               = HID_CSCP_BootSubclass,
+			.Protocol               = HID_CSCP_MouseBootProtocol,
 
 			.InterfaceStrIndex      = NO_DESCRIPTOR
 		},