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/zip_archive.cc b/runtime/zip_archive.cc
index ffab674..88c1f69 100644
--- a/runtime/zip_archive.cc
+++ b/runtime/zip_archive.cc
@@ -56,7 +56,7 @@
   name += " extracted in memory from ";
   name += zip_filename;
   std::unique_ptr<MemMap> map(MemMap::MapAnonymous(name.c_str(),
-                                                   NULL, GetUncompressedLength(),
+                                                   nullptr, GetUncompressedLength(),
                                                    PROT_READ | PROT_WRITE, false, false,
                                                    error_msg));
   if (map.get() == nullptr) {