Revert "Apply modernize-use-default to clang-tools-extra."

Breaks the build in GCC 4.7.2 (see
http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3 for example)

This reverts commit r250824.

llvm-svn: 250862
diff --git a/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp b/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
index 2a5196b..bad8043 100644
--- a/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
@@ -98,7 +98,7 @@
 public:
   CXXSystemIncludeInserterCheck(StringRef CheckName, ClangTidyContext *Context)
       : IncludeInserterCheckBase(CheckName, Context) {}
-  virtual ~CXXSystemIncludeInserterCheck() = default;
+  virtual ~CXXSystemIncludeInserterCheck() {}
 
   std::vector<StringRef> HeadersToInclude() const override { return {"set"}; }
   bool IsAngledInclude() const override { return true; }