Formatter: No space after & and * in front of ObjC message expressions.

1. let determineStarAmp() check of unary operators before checking for
   "is next '['". That check was added in r173150, and the test from that
   revision passes either way.

2. change determineStarAmp() to categorize '*' and '&' after '=' as unary
   operator.

3. don't let parseSquare() overwrite the type of a '*' or '&' before the start
   of an objc message expression if has the role of unary operator.

llvm-svn: 174489