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/intern_table.cc b/runtime/intern_table.cc
index 4c5fc81..a85d10f 100644
--- a/runtime/intern_table.cc
+++ b/runtime/intern_table.cc
@@ -194,7 +194,7 @@
       uint32_t string_idx = dex_file->GetIndexForStringId(*string_id);
       // GetResolvedString() contains a RB.
       mirror::String* image_string = dex_cache->GetResolvedString(string_idx);
-      if (image_string != NULL) {
+      if (image_string != nullptr) {
         return image_string;
       }
     }