Rename LiveIntervalAnalysis.h to LiveIntervals.h

Headers/Implementation files should be named after the class they
declare/define.

Also eliminated an `#include "llvm/CodeGen/LiveIntervalAnalysis.h"` in
favor of `class LiveIntarvals;`

llvm-svn: 320546
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index 6294881..572446c 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -18,7 +18,7 @@
 #include "SystemZSubtarget.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/LiveInterval.h"
-#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/LiveIntervals.h"
 #include "llvm/CodeGen/LiveVariables.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"