Support for cross compilation.

Refactor architecture specific files into arm and x86 name spaces. Make
assemblers and calling conventions use the factory pattern and an
instruction set specifier.

Change-Id: I20cd7aecacc1ae3d418221d98bbe1d69be9162a7
diff --git a/src/constants_x86.h b/src/constants_x86.h
index 36019ae..8712185 100644
--- a/src/constants_x86.h
+++ b/src/constants_x86.h
@@ -9,6 +9,7 @@
 #include "macros.h"
 
 namespace art {
+namespace x86 {
 
 enum Register {
   EAX = 0,
@@ -120,6 +121,7 @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(Instr);
 };
 
+}  // namespace x86
 }  // namespace art
 
 #endif  // ART_SRC_CONSTANTS_X86_H_