Add doInitialization/doFinalization to DataLayoutPass.

With this a DataLayoutPass can be reused for multiple modules.

Once we have doInitialization/doFinalization, it doesn't seem necessary to pass
a Module to the constructor.

Overall this change seems in line with the idea of making DataLayout a required
part of Module. With it the only way of having a DataLayout used is to add it
to the Module.

llvm-svn: 217548
diff --git a/llvm/lib/LTO/LTOCodeGenerator.cpp b/llvm/lib/LTO/LTOCodeGenerator.cpp
index 491975e..1b6f905 100644
--- a/llvm/lib/LTO/LTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/LTOCodeGenerator.cpp
@@ -471,7 +471,7 @@
 
   PassManager codeGenPasses;
 
-  codeGenPasses.add(new DataLayoutPass(mergedModule));
+  codeGenPasses.add(new DataLayoutPass());
 
   formatted_raw_ostream Out(out);