Rename OpCode.h -> DexOpcodes.h.

Also incorporate the former contents of OpCodeNames.h. This is a small
attempt to increase naming consistency in libdex. There will be a bit
more to come, in a follow-up.

Change-Id: Ia7ab06042dde2e19eda02ef1fee72fb4260e899d
diff --git a/vm/interp/Jit.c b/vm/interp/Jit.c
index cd5bfbd..e79b115 100644
--- a/vm/interp/Jit.c
+++ b/vm/interp/Jit.c
@@ -23,7 +23,7 @@
 #include "Jit.h"
 
 
-#include "libdex/OpCodeNames.h"
+#include "libdex/DexOpcodes.h"
 #include <unistd.h>
 #include <pthread.h>
 #include <sys/time.h>