Call .rs.dtor() when tearing down Scripts.

BUG=5186750

This allows us to properly reference count any globals (static or extern) that
need to potentially be cleaned up.

Change-Id: I03d2c38c1e7a4ca96c40003d2eeecb6f395d5835
diff --git a/driver/rsdBcc.h b/driver/rsdBcc.h
index 67929bc..5f83ed2 100644
--- a/driver/rsdBcc.h
+++ b/driver/rsdBcc.h
@@ -43,6 +43,8 @@
                         android::renderscript::Script *script);
 void rsdScriptInvokeInit(const android::renderscript::Context *dc,
                          android::renderscript::Script *script);
+void rsdScriptInvokeFreeChildren(const android::renderscript::Context *dc,
+                                 android::renderscript::Script *script);
 
 void rsdScriptSetGlobalVar(const android::renderscript::Context *,
                            const android::renderscript::Script *,