ART: Move JNI files to runtime/jni/ .

Test: Rely on TreeHugger.
Change-Id: I9cae11191ef1567ae9453be498882a7767285140
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index e85824d..b004566 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -71,9 +71,9 @@
 #include "heap-visit-objects-inl.h"
 #include "image.h"
 #include "intern_table.h"
-#include "java_vm_ext.h"
 #include "jit/jit.h"
 #include "jit/jit_code_cache.h"
+#include "jni/java_vm_ext.h"
 #include "mirror/class-inl.h"
 #include "mirror/object-inl.h"
 #include "mirror/object-refvisitor-inl.h"