Reduce namespace pollution.

This leaves us with just the mspace stuff and three libdex functions to clean
up. We deliberately expose the JII API, and I don't think there's anything we
can really do about the art_..._from_code stuff (and at least that starts with
"art_").

Change-Id: I77e58e8330cd2afeb496642302dfe3311e68091a
diff --git a/src/compiler/Dataflow.h b/src/compiler/Dataflow.h
index 1696e44..e810e52 100644
--- a/src/compiler/Dataflow.h
+++ b/src/compiler/Dataflow.h
@@ -20,6 +20,8 @@
 #include "Dalvik.h"
 #include "CompilerInternals.h"
 
+namespace art {
+
 typedef enum DataFlowAttributePos {
     kUA = 0,
     kUB,
@@ -151,4 +153,6 @@
 
 void oatMethodNullCheckElimination(CompilationUnit*);
 
+}  // namespace art
+
 #endif  // ART_SRC_COMPILER_DATAFLOW_H_