Fix missing include for iomanip in Settings.cpp

[JosiahWI]

Resolves: Compilation error in GCC 3.8 from undefined setw symbol. Authors: @JosiahWI

Summary of changes

• The iomanip header is included in Settings.cpp

Caveats

• None

On approval

Merge

[tobyplowy]

Builds and runs not like it wouldn't but still worth checking none the less.