Add completions to Common Lisp client

[russtoku]

I hope this helps a little to resolve issue #466.

Some issues:

• The candidates are identified as TEXT. I haven't figured out how to at least annotate them as symbols or something that would indicate that they are from from Swank.
• The candidate list returned from Swank is based the first letter typed. 'lo' and 'la' would share the same list of candidates.
• If you trigger omnicompletion after typing say 'lo', you'll get an error message but the completion pop-up window is not affected.

Suggestions welcome.

[LordMZTE]

This is awesome! Apart from what you stated already, I have 3 more criticizms:

• The Conjure output window is spammed a little during completion. It'd be great if output from completions wasn't sent to it.
• An error occurs when completing a package, for example triggering a completion here: uiop:| (where | represents the cursor) causes this error to appear:

Error executing vim.schedule lua callback: ...ker/opt/conjure/lua/conjure/client/common-lisp/swank.lua:173: too many results to unpack
stack traceback:
	[C]: in function 'unpack'
	...ker/opt/conjure/lua/conjure/client/common-lisp/swank.lua:173: in function 'dispatch'
	...ker/opt/conjure/lua/conjure/client/common-lisp/swank.lua:213: in function 'parse_separated_list'
	...ker/opt/conjure/lua/conjure/client/common-lisp/swank.lua:232: in function 'parse_result'
	...ker/opt/conjure/lua/conjure/client/common-lisp/swank.lua:249: in function ''
	vim/_editor.lua: in function <vim/_editor.lua:0>

• This may be a limitation with swank, but currently, completions are shown which won't work due to being declared in another package. For example, your code would suggest run-program whereas that function needs to be refered to by uiop:run-program.

Thanks for you great work! This is really good already!

[Olical]

Tried it locally and I got some completions! I had to trigger omnicomplete though with <c-x><c-o> which I found odd.

[Olical]

A fun error if I trigger omnicompletion with no text on the line:

I think there's an unpack somewhere in our lua and it's being asked to unpack too many values. I didn't know there was a limit so The More You Know! I'll see if I can find it.

[Olical]

I've replaced the unpack in question with (str.join (a.map string.char stack)) and it can now handle any size. So we should avoid using unpack for unbounded tables or at least tables we think could get very large. Merged to develop!

[russtoku]

Yes, that unpack was the cause of the error. Thanks for that fix.
I'm still trying to work through some of the short-comings mentioned but I'm glad we've gotten thing this far.