Fix Clang-tidy modernize-use-nullptr warnings in source directories and generated files; other minor cleanups.

Patch by Eugene Zelenko!

Differential Revision: http://reviews.llvm.org/D13321

llvm-svn: 249482
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index 87cd222..49586f4 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -29,6 +29,7 @@
 #include <algorithm>
 #include <cstdarg>
 #include <cstdlib>
+
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//
@@ -81,7 +82,6 @@
   return new RandomNumberGenerator(Salt);
 }
 
-
 /// getNamedValue - Return the first global value in the module with
 /// the specified name, of arbitrary type.  This method returns null
 /// if a global with the specified name is not found.
@@ -481,7 +481,7 @@
 PICLevel::Level Module::getPICLevel() const {
   auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("PIC Level"));
 
-  if (Val == NULL)
+  if (!Val)
     return PICLevel::Default;
 
   return static_cast<PICLevel::Level>(