Cleanup LLVMTextAPI headers

Based on the output of iwyu. A full rebuild of llvm-project doesn't exhibit any
significant false dependencies.

The impact on preprocessed output is larger than expected, given the small
amount of changes

$ clang++ -E  -Iinclude -I../llvm/include ../llvm/lib/TextAPI/*.cpp -std=c++14 -fno-rtti -fno-exceptions | wc -l
before: 635319
After: 643716

Discourse thread on the topic: https://llvm.discourse.group/t/include-what-you-use-include-cleanup

llvm/include/llvm/TextAPI/InterfaceFile.h

@@ -19,11 +19,7 @@
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator.h"
-#include "llvm/BinaryFormat/MachO.h"
-#include "llvm/BinaryFormat/Magic.h"
 #include "llvm/Support/Allocator.h"
-#include "llvm/Support/Error.h"
-#include "llvm/TextAPI/Architecture.h"
 #include "llvm/TextAPI/ArchitectureSet.h"
 #include "llvm/TextAPI/PackedVersion.h"
 #include "llvm/TextAPI/Platform.h"

llvm/include/llvm/TextAPI/Target.h

@@ -9,13 +9,15 @@
 #ifndef LLVM_TEXTAPI_TARGET_H
 #define LLVM_TEXTAPI_TARGET_H
 
-#include "llvm/ADT/Triple.h"
 #include "llvm/Support/Error.h"
 #include "llvm/TextAPI/Architecture.h"
 #include "llvm/TextAPI/ArchitectureSet.h"
 #include "llvm/TextAPI/Platform.h"
 
 namespace llvm {
+
+class Triple;
+
 namespace MachO {
 
 // This is similar to a llvm Triple, but the triple doesn't have all the

llvm/lib/TextAPI/Architecture.cpp

@@ -15,7 +15,7 @@
 #include "llvm/ADT/Triple.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/TextAPI/ArchitectureSet.h"
+#include "llvm/Support/ErrorHandling.h"
 
 namespace llvm {
 namespace MachO {

llvm/lib/TextAPI/PackedVersion.cpp

@@ -11,7 +11,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/TextAPI/PackedVersion.h"
-#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/Format.h"

llvm/lib/TextAPI/Target.cpp

@@ -7,11 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/TextAPI/Target.h"
-#include "llvm/ADT/SmallString.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
-#include "llvm/Support/Format.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace llvm {

llvm/lib/TextAPI/TextStubCommon.h

@@ -16,9 +16,9 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/TextAPI/Architecture.h"
-#include "llvm/TextAPI/ArchitectureSet.h"
 #include "llvm/TextAPI/InterfaceFile.h"
-#include "llvm/TextAPI/PackedVersion.h"
+#include "llvm/TextAPI/Platform.h"
+#include "llvm/TextAPI/Target.h"
 
 using UUID = std::pair<llvm::MachO::Target, std::string>;
 
@@ -28,6 +28,11 @@ LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(UUID)
 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(FlowStringRef)
 
 namespace llvm {
+
+namespace MachO {
+    class ArchitectureSet;
+    class PackedVersion;
+}
 namespace yaml {
 
 template <> struct ScalarTraits<FlowStringRef> {