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/interpreter/interpreter_common.h b/runtime/interpreter/interpreter_common.h
index 0e0d56a..dbedc16 100644
--- a/runtime/interpreter/interpreter_common.h
+++ b/runtime/interpreter/interpreter_common.h
@@ -367,9 +367,9 @@
       uint32_t raw_value = shadow_frame.GetVReg(i);
       Object* ref_value = shadow_frame.GetVRegReference(i);
       oss << StringPrintf(" vreg%u=0x%08X", i, raw_value);
-      if (ref_value != NULL) {
+      if (ref_value != nullptr) {
         if (ref_value->GetClass()->IsStringClass() &&
-            ref_value->AsString()->GetCharArray() != NULL) {
+            ref_value->AsString()->GetCharArray() != nullptr) {
           oss << "/java.lang.String \"" << ref_value->AsString()->ToModifiedUtf8() << "\"";
         } else {
           oss << "/" << PrettyTypeOf(ref_value);