Fix Python3-XPC sendDREFs issue

[DisgracedPilot]

Resolves #198, where the Python3 version fails when using sendDREF / sendDREFs for a dataref that requires multiple values. Issue is that the array of dataref values is passed directly into the pack function instead of passing each array element as a separate argument. Solution due to @jamesdunham in the issue comments.

[bgeiger99]

I came across this issue recently and implemented the same fix with one difference. The second change (Line 316) should be reverted to the original code - in that case, value would not be a list and struct.pack will error trying to unpack a non-iterable.

buffer += struct.pack(fmt.encode(), len(dref), dref.encode(), 1, value) # reverted from *value

[jason-watkins]

Sorry for the long delay. I don't get much time to work on this project anymore. Could either of you explain exactly what this change does? My Python is a little rusty and I'm having trouble evaluating who is correct here.

[bgeiger99]

Sure - Line 309 is checking to see if value is a list of values (i.e. [1,2,3..]) or a single number (i.e. 7).

If it is a list of values, Line 313 is executed. The change on Line 313 is correct because *value is the correct way to unpack a list of values into the call to struct.

If value is a single number, Line 315 is executed. Line 315 is not correct because this part of the code expects a single value (just a number, not a list). Therefore, the call to struct should use value instead of *value (because value is just a number and not a list that needs unpacking). Additionally, the argument before value is 1, signifying only a single number is expected.