add a delete function

include/lassospkit_memcache.inc.php

@@ -67,4 +67,11 @@ class LassoSPKitMemCache {
         }
         return $instance->get($key);
     }
+    function delete($key) {
+        $instance = LassoSPKitMemCache::getInstance();
+        if (! $instance) {
+            lassospkit_errlog("LassoSPKitMemCache: could not delete key " . var_export($key,1) . ", no instance present");
+        }
+        return $instance->delete($key);
+    }
 }