[rebranch] Add missing llvm/IR/Module.h include

`llvm/IR/Module.h` was presumably being transitively included
previously.

lib/IRGen/GenConcurrency.cpp

@@ -31,6 +31,7 @@
 #include "swift/AST/ProtocolConformanceRef.h"
 #include "swift/ABI/MetadataValues.h"
 #include "swift/Basic/Assertions.h"
+#include "llvm/IR/Module.h"
 
 using namespace swift;
 using namespace irgen;

lib/LLVMPasses/LLVMInlineTree.cpp

@@ -27,6 +27,7 @@
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/CommandLine.h"