Replace NULL with nullptr

Also fixed some lines that were too long, and a few other minor
details.

Change-Id: I6efba5fb6e03eb5d0a300fddb2a75bf8e2f175cb
diff --git a/runtime/indirect_reference_table-inl.h b/runtime/indirect_reference_table-inl.h
index e571a0e..639be51 100644
--- a/runtime/indirect_reference_table-inl.h
+++ b/runtime/indirect_reference_table-inl.h
@@ -31,7 +31,7 @@
 // Returns "false" if something looks bad.
 inline bool IndirectReferenceTable::GetChecked(IndirectRef iref) const {
   if (UNLIKELY(iref == nullptr)) {
-    LOG(WARNING) << "Attempt to look up NULL " << kind_;
+    LOG(WARNING) << "Attempt to look up nullptr " << kind_;
     return false;
   }
   if (UNLIKELY(GetIndirectRefKind(iref) == kHandleScopeOrInvalid)) {