Test/fixes to handle NULL pointer for unique_ptr/auto_ptr

Also add missing unique_ptr tests for Lua and Racket.

Examples/test-suite/mzscheme/li_std_auto_ptr_runme.scm

@@ -74,6 +74,12 @@
 (set! kini '()) (gc) ; Should not fail, even though already deleted
 (checkCount 0)
 
+(define null '())
+(takeKlassAutoPtr null)
+(takeKlassAutoPtr (make-null))
+(checkCount 0)
+
+
 ; auto_ptr as output
 (define k1 (makeKlassAutoPtr "first"))
 (define k2 (makeKlassAutoPtr "second"))
@@ -88,4 +94,7 @@
 (set! k2 '()) (gc)
 (checkCount 0)
 
+(unless (null? (makeNullAutoPtr))
+  (error "null failure"))
+
 (exit 0)