Fix bug in SpaceAroundBlockBraces that desetroys code in -a mode.

Multi-line block braces cause autocorrect to behave badly. The solution is to allow multi-line block braces regardless of configuration.

Fixes #645.
Merge pull request #646 from jonas054/fix_space_around_block_braces

Fix bug in SpaceAroundBlockBraces that desetroys code in -a mode.