[NFC] Header cleanup

Removed some unused headers, replaced some headers with forward class declarations.

Found using simple scripts like this one:
clear && ack --cpp -l '#include "llvm/ADT/IndexedMap.h"' | xargs grep -L 'IndexedMap[<]' | xargs grep -n --color=auto 'IndexedMap'

Patch by Eugene Kosov <claprix@yandex.ru>

Differential Revision: http://reviews.llvm.org/D19219

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 266595
diff --git a/llvm/lib/CodeGen/CriticalAntiDepBreaker.h b/llvm/lib/CodeGen/CriticalAntiDepBreaker.h
index ac0dac6..678779f 100644
--- a/llvm/lib/CodeGen/CriticalAntiDepBreaker.h
+++ b/llvm/lib/CodeGen/CriticalAntiDepBreaker.h
@@ -19,17 +19,15 @@
 #include "AntiDepBreaker.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
-#include "llvm/CodeGen/MachineFrameInfo.h"
-#include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterClassInfo.h"
 #include "llvm/CodeGen/ScheduleDAG.h"
-#include <map>
 
 namespace llvm {
 class RegisterClassInfo;
 class TargetInstrInfo;
 class TargetRegisterInfo;
+class MachineFunction;
 
 class LLVM_LIBRARY_VISIBILITY CriticalAntiDepBreaker : public AntiDepBreaker {
     MachineFunction& MF;