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

llvm/examples/ExceptionDemo/ExceptionDemo.cpp

@@ -1977,7 +1977,7 @@ int main(int argc, char *argv[]) {
     // Start with registering info about how the
     // target lays out data structures.
     module->setDataLayout(executionEngine->getDataLayout());
-    fpm.add(new llvm::DataLayoutPass(module));
+    fpm.add(new llvm::DataLayoutPass());
 
     // Optimizations turned on
 #ifdef ADD_OPT_PASSES