Add isRegSequence property.

This patch adds a new property: isRegSequence and the related target hooks: 
TargetIntrInfo::getRegSequenceInputs and 
TargetInstrInfo::getRegSequenceLikeInputs to specify that a target specific
instruction is a (kind of) REG_SEQUENCE.

<rdar://problem/12702965>

llvm-svn: 215394
diff --git a/llvm/utils/TableGen/CodeGenInstruction.h b/llvm/utils/TableGen/CodeGenInstruction.h
index f143875..59a4d21 100644
--- a/llvm/utils/TableGen/CodeGenInstruction.h
+++ b/llvm/utils/TableGen/CodeGenInstruction.h
@@ -253,6 +253,7 @@
     bool hasExtraDefRegAllocReq : 1;
     bool isCodeGenOnly : 1;
     bool isPseudo : 1;
+    bool isRegSequence : 1;
 
     std::string DeprecatedReason;
     bool HasComplexDeprecationPredicate;