Implement code completion for Objective-C method declarations and

Implement code completion for Objective-C method declarations and
definitions, e.g., after

  -

or

  - (id)

we'll find all of the "likely" instance methods that one would want to
declare or define at this point. In the latter case, we only produce
results whose return types match "id".

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@100587 91177308-0d34-0410-b5e6-96231b3b80d8