Simplify updating queue entries

The erase/insert pattern can be replaced by a single method that
updates an existing entry's timer, or inserting if it doesn't exist.

This has much less impact than the libtorrent change it's based on,
but might as well be consistent.

src/core/curl_get.cc

@@ -83,8 +83,7 @@ CurlGet::start() {
     // Normally libcurl should handle the timeout. But sometimes that doesn't
     // work right so we do a fallback timeout that just aborts the transfer.
     m_taskTimeout.slot() = std::bind(&CurlGet::receive_timeout, this);
-    priority_queue_erase(&taskScheduler, &m_taskTimeout);
-    priority_queue_insert(&taskScheduler, &m_taskTimeout, cachedTime + rak::timer::from_seconds(m_timeout + 5));
+    priority_queue_update(&taskScheduler, &m_taskTimeout, cachedTime + rak::timer::from_seconds(m_timeout + 5));
   }
 
   curl_easy_setopt(m_handle, CURLOPT_FORBID_REUSE,   (long)1);

src/core/curl_stack.cc

@@ -262,8 +262,7 @@ int
 CurlStack::set_timeout(void* handle, long timeout_ms, void* userp) {
   CurlStack* stack = (CurlStack*)userp;
 
-  priority_queue_erase(&taskScheduler, &stack->m_taskTimeout);
-  priority_queue_insert(&taskScheduler, &stack->m_taskTimeout, cachedTime + rak::timer::from_milliseconds(timeout_ms));
+  priority_queue_update(&taskScheduler, &stack->m_taskTimeout, cachedTime + rak::timer::from_milliseconds(timeout_ms));
 
   return 0;
 }

src/core/view.cc

@@ -145,8 +145,7 @@ struct view_downloads_filter : std::unary_function<Download*, bool> {
 
 void
 View::emit_changed() {
-  priority_queue_erase(&taskScheduler, &m_delayChanged);
-  priority_queue_insert(&taskScheduler, &m_delayChanged, cachedTime);
+  priority_queue_update(&taskScheduler, &m_delayChanged, cachedTime);
 }
 
 void