Replace `typedef A B` with `using B = A`. NFC.

I did this using Perl.

Differential Revision: https://reviews.llvm.org/D60003

llvm-svn: 357372
diff --git a/lld/ELF/CallGraphSort.cpp b/lld/ELF/CallGraphSort.cpp
index 8550177..10fc6bf 100644
--- a/lld/ELF/CallGraphSort.cpp
+++ b/lld/ELF/CallGraphSort.cpp
@@ -92,8 +92,8 @@
 constexpr uint64_t MAX_CLUSTER_SIZE = 1024 * 1024;
 } // end anonymous namespace
 
-typedef std::pair<const InputSectionBase *, const InputSectionBase *>
-    SectionPair;
+using SectionPair =
+    std::pair<const InputSectionBase *, const InputSectionBase *>;
 
 // Take the edge list in Config->CallGraphProfile, resolve symbol names to
 // Symbols, and generate a graph between InputSections with the provided