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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217548 91177308-0d34-0410-b5e6-96231b3b80d8

examples/Kaleidoscope/Chapter6/toy.cpp

@@ -951,7 +951,7 @@ int main() {
   // Set up the optimizer pipeline.  Start with registering info about how the
   // target lays out data structures.
   TheModule->setDataLayout(TheExecutionEngine->getDataLayout());
-  OurFPM.add(new DataLayoutPass(TheModule));
+  OurFPM.add(new DataLayoutPass());
   // Provide basic AliasAnalysis support for GVN.
   OurFPM.add(createBasicAliasAnalysisPass());
   // Do simple "peephole" optimizations and bit-twiddling optzns.