Ensure I'm using <optional> everywhere I should.

Analyser/Static/AmstradCPC/StaticAnalyser.cpp

@@ -16,6 +16,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <optional>
 #include <unordered_set>
 
 namespace {

Machines/Acorn/Archimedes/CMOSRAM.hpp

@@ -12,6 +12,7 @@
 #include "Outputs/Log.hpp"
 
 #include <array>
+#include <optional>
 
 namespace Archimedes {
 

Machines/Commodore/Plus4/Plus4.cpp

@@ -34,6 +34,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <optional>
 #include <vector>
 
 using namespace Commodore;

Machines/Commodore/Vic-20/Vic20.cpp

@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <array>
 #include <cstdint>
+#include <optional>
 
 namespace {
 using Logger = Log::Logger<Log::Source::Vic20>;

Machines/Utility/ROMCatalogue.cpp

@@ -13,6 +13,7 @@
 #include <cstdlib>
 #include <iomanip>
 #include <locale>
+#include <optional>
 #include <sstream>
 
 using namespace ROM;

OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm

@@ -13,6 +13,7 @@
 #import "NSData+StdVector.h"
 #import "NSData+CRC32.h"
 
+#include <optional>
 #include <string>
 
 namespace {

Outputs/CRT/CRT.cpp

@@ -14,6 +14,7 @@
 #include <cassert>
 #include <cmath>
 #include <cstdarg>
+#include <optional>
 
 using namespace Outputs::CRT;
 using Logger = Log::Logger<Log::Source::CRT>;

Outputs/OpenGL/ScanTarget.hpp

@@ -24,6 +24,7 @@
 #include <chrono>
 #include <list>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 

Storage/Data/ZX8081.cpp

@@ -8,6 +8,8 @@
 
 #include "ZX8081.hpp"
 
+#include <optional>
+
 using namespace Storage::Data::ZX8081;
 
 namespace {

Storage/Disk/Encodings/MFM/Encoder.cpp

@@ -14,7 +14,7 @@
 #include "Numeric/BitSpread.hpp"
 
 #include <cassert>
-#include <set>
+#include <optional>
 
 using namespace Storage::Encodings::MFM;
 

Storage/Disk/Parsers/FAT.cpp

@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <iostream>
+#include <optional>
 
 using namespace Storage::Disk;
 

Storage/Tape/Parsers/ZX8081.hpp

@@ -12,6 +12,7 @@
 
 #include "Storage/Data/ZX8081.hpp"
 
+#include <optional>
 #include <string>
 #include <vector>
 #include <cstdint>