Initiate a constant propagation pass in the optimizing compiler.

- Perform constant folding on int and long additions and subtractions in
  the optimizing compiler.
- Apply constant folding to conditions and comparisons.

Change-Id: Ic88783a3c975fda777c74c531e257fa777be42eb
diff --git a/compiler/Android.mk b/compiler/Android.mk
index 3d433d5..35cddf9 100644
--- a/compiler/Android.mk
+++ b/compiler/Android.mk
@@ -90,6 +90,7 @@
 	optimizing/code_generator_arm.cc \
 	optimizing/code_generator_x86.cc \
 	optimizing/code_generator_x86_64.cc \
+	optimizing/constant_propagation.cc \
 	optimizing/dead_code_elimination.cc \
 	optimizing/graph_checker.cc \
 	optimizing/graph_visualizer.cc \