swift234

[CodeCompletion] Don't complete entire call patterns inside existing calls

Peek at the token following the code completion location to decide
whether or not to provide completions for entire call patterns.  When
the next token looks like it's part of an existing call we don't show
the patterns because they will "push out" the existing arguments.

We should now get:
  Foo<here> =>  (blah, blah)
  Foo(<here> =>  ['(']blah, blah)
  Foo(<here>) => ['(']blah, blah[')']
  Foo(<here>, blah) => just complete the values for arg1**
  Foo(<here>blah, blah) => just complete the values for arg1

** A further improvement will be to add the argument label completion
for the first argument (if applicable) when we aren't showing a full
call pattern.

rdar://problem/22804670

Swift SVN r32765