Space trim and other unit tests. General space clean up.

The space unit tests now include checks on space invariants, in
particular relating to footprint and size.
Out-of-date comments have been removed.
This patch adds PrettySize and PrettyDuration methods to make these
strings more human readable.

Change-Id: I6bc05b2db0d0115b97d666b832fce57bcdd2e091
diff --git a/src/dex2oat.cc b/src/dex2oat.cc
index cd977b5..171ae3a 100644
--- a/src/dex2oat.cc
+++ b/src/dex2oat.cc
@@ -96,7 +96,7 @@
 
   ~Dex2Oat() {
     delete runtime_;
-    LOG(INFO) << "dex2oat took " << NsToMs(NanoTime() - start_ns_) << "ms";
+    LOG(INFO) << "dex2oat took " << PrettyDuration(NanoTime() - start_ns_);
   }
 
   // Make a list of descriptors for classes to include in the image