[DebugInfo] Move several private headers to include directory

This patch moved the following files in lib/CodeGen/AsmPrinter/
  AsmPrinterHandler.h
  DbgEntityHistoryCalculator.h
  DebugHandlerBase.h
to include/llvm/CodeGen directory.

Such a change will enable Target to extend DebugHandlerBase
and emit Target specific debug info sections.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D55755

llvm-svn: 349564
diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
index bb2fa7d..0986782 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgEntityHistoryCalculator.cpp
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "DbgEntityHistoryCalculator.h"
+#include "llvm/CodeGen/DbgEntityHistoryCalculator.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"