[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

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/IR/ConstantFold.h b/llvm/lib/IR/ConstantFold.h
index 2a272da4337..9b0a937c84d 100644
--- a/llvm/lib/IR/ConstantFold.h
+++ b/llvm/lib/IR/ConstantFold.h
@@ -19,9 +19,8 @@
 #ifndef LLVM_LIB_IR_CONSTANTFOLD_H
 #define LLVM_LIB_IR_CONSTANTFOLD_H
 
-#include "llvm/ADT/ArrayRef.h"
-
 namespace llvm {
+template <typename T> class ArrayRef;
   class Value;
   class Constant;
   class Type;