[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, 1 deletions

diff --git a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.h b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.h
index 4a4d33b3689..ec05a66c2df 100644
--- a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.h
+++ b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.h
@@ -16,13 +16,13 @@
 #define LLVM_LIB_TARGET_X86_UTILS_X86SHUFFLEDECODE_H
 
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/ArrayRef.h"
 
 //===----------------------------------------------------------------------===//
 //  Vector Mask Decoding
 //===----------------------------------------------------------------------===//
 
 namespace llvm {
+template <typename T> class ArrayRef;
 class MVT;
 
 enum { SM_SentinelUndef = -1, SM_SentinelZero = -2 };