Delete the CommonSection class.

With the current infrastructure it can be just an ordinary
InputSection like the real .bss sections.

llvm-svn: 286234
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 7f244d9..5084b74 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -287,7 +287,7 @@
   if (In<ELFT>::BuildId)
     Symtab<ELFT>::X->Sections.push_back(In<ELFT>::BuildId);
 
-  CommonSection<ELFT> *Common = make<CommonSection<ELFT>>();
+  InputSection<ELFT> *Common = createCommonSection<ELFT>();
   if (!Common->Data.empty()) {
     In<ELFT>::Common = Common;
     Symtab<ELFT>::X->Sections.push_back(Common);