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/base/hex_dump.cc b/runtime/base/hex_dump.cc
index 5423ff0..bce6b53 100644
--- a/runtime/base/hex_dump.cc
+++ b/runtime/base/hex_dump.cc
@@ -27,7 +27,7 @@
     return;
   }
 
-  if (address_ == NULL) {
+  if (address_ == nullptr) {
     os << "00000000:";
     return;
   }