clang-format: Improve detection of function types.

This fixes an incorrect detection that led to a formatting error.
Before:
  some_var = function (*some_pointer_var)[0];
After:
  some_var = function(*some_pointer_var)[0];

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@186402 91177308-0d34-0410-b5e6-96231b3b80d8