Optimizing: Improve constant folding + DCE for inlining.

Run constant folding before DCE in inliner to eliminate more
code that can prevent inlining. Improve the constant folding
to evaluate Equals and NotEquals for null inputs.

Change-Id: I876ffb903ef39484370b6c8793f0f8467a977362
diff --git a/compiler/optimizing/inliner.cc b/compiler/optimizing/inliner.cc
index 353881e..c9319f5 100644
--- a/compiler/optimizing/inliner.cc
+++ b/compiler/optimizing/inliner.cc
@@ -406,8 +406,8 @@
     &type_propagation,
     &sharpening,
     &simplify,
-    &dce,
     &fold,
+    &dce,
   };
 
   for (size_t i = 0; i < arraysize(optimizations); ++i) {