Include what you use: Optional and Hashing

Add a few includes of Optional.h and Hashing.h. These files are failing
ot build in the "next" branch due to changes in llvm's own includes, but
it's general goodness to include them on main as well.

include/swift/ABI/TypeIdentity.h

@@ -19,6 +19,7 @@
 #define SWIFT_ABI_TYPEIDENTITY_H
 
 #include "swift/Basic/LLVM.h"
+#include <llvm/ADT/Optional.h>
 #include <llvm/ADT/StringRef.h>
 
 namespace swift {

include/swift/Basic/Fingerprint.h

@@ -15,6 +15,7 @@
 
 #include "swift/Basic/StableHasher.h"
 #include "llvm/ADT/Hashing.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 

include/swift/Basic/SourceLoc.h

@@ -20,6 +20,7 @@
 #include "swift/Basic/Debug.h"
 #include "swift/Basic/LLVM.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/SMLoc.h"
 #include <functional>

include/swift/Basic/Statistic.h

@@ -13,6 +13,7 @@
 #ifndef SWIFT_BASIC_STATISTIC_H
 #define SWIFT_BASIC_STATISTIC_H
 
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Support/Timer.h"

include/swift/Demangling/ManglingUtils.h

@@ -13,6 +13,7 @@
 #ifndef SWIFT_DEMANGLING_MANGLINGUTILS_H
 #define SWIFT_DEMANGLING_MANGLINGUTILS_H
 
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 #include "swift/Demangling/NamespaceMacros.h"
 #include "swift/Demangling/Punycode.h"

include/swift/Remote/MemoryReader.h

@@ -20,6 +20,7 @@
 
 #include "swift/Remote/RemoteAddress.h"
 #include "swift/SwiftRemoteMirror/MemoryReaderInterface.h"
+#include "llvm/ADT/Optional.h"
 
 #include <cstring>
 #include <functional>