Sticky mark bits "generational" GC

Sticky mark bits GC. Sticky mark bits implemented using allocation stack which enables us to use the previous GC live bitmap as the mark bitmap.

Removed heap_end_ since checking versus it caused more overhead than it saved.

Removed check for impossible allocations at the start of AllocObject since these allocations will just fall through and fail anyways.
These allocations do not happen often enough for it to be worth checking for.

A bunch of constant optimization performance improvements.

Pre locking regression benchmark improvements:
Deltablue: ~0.3 sec runtime.
CaffeineMark: ~300 total score due to improved string score.

Change-Id: I15016f1ae7fdf76fc3aadb5774b527bf802d9701
diff --git a/src/utils.h b/src/utils.h
index 851c6b1..2846dad 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -314,6 +314,12 @@
 bool IsValidDexFilename(const std::string& filename);
 bool IsValidOatFilename(const std::string& filename);
 
+class IdentityFunctor {
+ public:
+  template <typename T>
+  inline T operator () (T t) const { return t; }
+};
+
 }  // namespace art
 
 #endif  // ART_SRC_UTILS_H_