fixes to support node >= v0.7.9

Use the new uv_ref()/uv_unref() API for node >= v0.7.9, and remove a couple
unnecessary instances of uv_ref()/uv_unref() where only uv_queue_work() was
being used.

src/async.h

@@ -2,6 +2,7 @@
 #define NODE_SQLITE3_SRC_ASYNC_H
 
 #include "threading.h"
+#include <node_version.h>
 
 #if defined(NODE_SQLITE3_BOOST_THREADING)
 #include <boost/thread/mutex.hpp>
@@ -35,7 +36,11 @@ public:
         rows.swap(async->data);
         NODE_SQLITE3_MUTEX_UNLOCK(&async->mutex)
         for (unsigned int i = 0, size = rows.size(); i < size; i++) {
+#if NODE_VERSION_AT_LEAST(0, 7, 9)
+            uv_unref((uv_handle_t *)&async->watcher);
+#else
             uv_unref(uv_default_loop());
+#endif
             async->callback(async->parent, rows[i]);
         }
     }
@@ -58,7 +63,11 @@ public:
 
     void add(Item* item) {
         // Make sure node runs long enough to deliver the messages.
+#if NODE_VERSION_AT_LEAST(0, 7, 9)
+        uv_ref((uv_handle_t *)&watcher);
+#else
         uv_ref(uv_default_loop());
+#endif
         NODE_SQLITE3_MUTEX_LOCK(&mutex);
         data.push_back(item);
         NODE_SQLITE3_MUTEX_UNLOCK(&mutex)

src/database.h

@@ -38,13 +38,11 @@ public:
         Baton(Database* db_, Handle<Function> cb_) :
                 db(db_), status(SQLITE_OK) {
             db->Ref();
-            uv_ref(uv_default_loop());
             request.data = this;
             callback = Persistent<Function>::New(cb_);
         }
         virtual ~Baton() {
             db->Unref();
-            uv_unref(uv_default_loop());
             callback.Dispose();
         }
     };

src/statement.h

@@ -86,7 +86,6 @@ public:
 
         Baton(Statement* stmt_, Handle<Function> cb_) : stmt(stmt_) {
             stmt->Ref();
-            uv_ref(uv_default_loop());
             request.data = this;
             callback = Persistent<Function>::New(cb_);
         }
@@ -96,7 +95,6 @@ public:
                 DELETE_FIELD(field);
             }
             stmt->Unref();
-            uv_unref(uv_default_loop());
             callback.Dispose();
         }
     };