clang-format: Add spaces between lambdas and comments.

Before:
  void f() {
    bar([]() {}// Does not respect SpacesBeforeTrailingComments
        );
  }

After:
  void f() {
    bar([]() {} // Does not respect SpacesBeforeTrailingComments
        );
  }

This fixes llvm.org/PR19017.

llvm-svn: 203466