[clang-format] Respect BreakBeforeClosingBrace while calculating length

Summary:
This patch makes `getLengthToMatchingParen` respect the `BreakBeforeClosingBrace`
ParenState for matching scope closers. In order to distinguish between paren states
introduced by real vs. fake parens, I've added the token opening the ParensState
to that struct.

Reviewers: djasper

Reviewed By: djasper

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D46519

llvm-svn: 331857