Handle nested ObjC calls.

Properly handle annotation contexts while calculating extra information
for each token. This enable nested ObjC calls and thus solves (most of)
llvm.org/PR15164. E.g., we can now format:

[contentsContainer replaceSubview:[subviews objectAtIndex:0]
                             with:contentsNativeView];

Also fix a problem with the formatting of types in casts as this was
trivial now.

llvm-svn: 174498