Merge OutputSectionBase and OutputSection. NFC.

Now that all special sections are SyntheticSections, we only need one
OutputSection class.

llvm-svn: 296127
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index 47dd62e..405c44a 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/lld/ELF/SymbolTable.cpp
@@ -397,7 +397,7 @@
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addSynthetic(StringRef N,
-                                        const OutputSectionBase *Section,
+                                        const OutputSection *Section,
                                         uintX_t Value, uint8_t StOther) {
   Symbol *S;
   bool WasInserted;