[clang-format] Add SpaceBeforeBrackets

Summary: Adds a new option SpaceBeforeBrackets to add spaces before brackets (i.e. int a[23]; -> int a [23];)  This is present as an option in the Visual Studio C++ code formatting settings, but there was no matching setting in clang-format.

Reviewers: djasper, MyDeveloperDay, mitchell-stellar

Reviewed By: MyDeveloperDay

Subscribers: llvm-commits, cfe-commits, klimek

Patch by: Anteru

Tags: #clang, #clang-format, #llvm

Differential Revision: https://reviews.llvm.org/D6920