Allow us to better guess the context of an unwrapped line.

This gives us the ability to guess better defaults for whether a *
between identifiers is a pointer dereference or binary operator.

Now correctly formats:
void f(a *b);
void f() { f(a * b); }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173243 91177308-0d34-0410-b5e6-96231b3b80d8