Revert "Fix Clang-tidy modernize-deprecated-headers warnings in remaining files; other minor fixes."

This reverts commit r265454 since it broke the build.  E.g.:

  http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA-incremental_build/22413/

llvm-svn: 265459
diff --git a/llvm/unittests/ADT/SmallStringTest.cpp b/llvm/unittests/ADT/SmallStringTest.cpp
index b044378..995ef8e 100644
--- a/llvm/unittests/ADT/SmallStringTest.cpp
+++ b/llvm/unittests/ADT/SmallStringTest.cpp
@@ -12,9 +12,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/SmallString.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
 #include "gtest/gtest.h"
+#include <climits>
+#include <cstring>
+#include <stdarg.h>
 
 using namespace llvm;
 
@@ -203,4 +204,4 @@
   EXPECT_EQ( 1, SmallString<10>("V8_q0").compare_numeric("V1_q0"));
 }
 
-} // end anonymous namespace
+}