Implement automatic bracket insertion for Objective-C class message

sends. These are far trickier than instance messages, because we
typically have something like

  NSArray alloc]

where it appears to be a declaration of a variable named "alloc" up
until we see the ']' (or a ':'), and at that point we can't backtrace.
So, we use a combination of syntactic and semantic disambiguation to
treat this as a message send only when the type is an Objective-C type
and it has the syntax of a class message send (which would otherwise
be ill-formed).

llvm-svn: 114057