Remove undocumented structuralCast in std.exception
fix Issue 4999 - Add Kenji Hara's adaptTo() to Phobos

Add structuralCast and structuralDownCast in std.typecons
Rename structuralCast to wrap, and structuralDownCast to unwrap
Make Tuple.opAssign CTFEable
Detab and strip std.bitmanip.
Space after if
Merge pull request #1325 from youkei/fix_10218

Issue 10218 - std.typecons.opAssign is not CTFEable
Fixes Issue 4124 - Implement toString for BitArray.
Merge pull request #1144 from AndrejMitrovic/Fix4124

Issue 4124 - Implement toString for BitArray.
Merge pull request #1265 from 9rnsr/structuralCast

Issue 4999 - Add Kenji Hara's adaptTo() to Phobos