Pulling formatFirstToken one level up.

This prepares the code for single line optimizations and changes the
dependencies between single-line-formats to the indent of the first
token.

Conceptually, the first token is "between" the lines anyway, as the
whitespace for the first token includes the previous end-of-line, which
needs to be escaped when inside a preprocessor directive.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172083 91177308-0d34-0410-b5e6-96231b3b80d8