Handle bracket insertion for Objective-C class messages in a very

Handle bracket insertion for Objective-C class messages in a very
narrow, almost useless case where we're inside a parenthesized
expression, e.g.,

  (NSArray alloc])

The solution to the general case still eludes me.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@114039 91177308-0d34-0410-b5e6-96231b3b80d8