Fix wrong assertion mAddedEasyRequests.size() >= (size_t)mRunningHandles

Rename check_run_count to check_msg_queue, because the whole 'run count'
approach is flawed anyway (the author of libcurl told me that THE way
to check for finished curl handles is to just call curl_multi_info_read
every time: it's extremely fast. Any test that attempts to avoid that
call is nonsense anyway.

The reason the assertion failed might have been caused by the fact
that we're comparing the current number of easy handles with the
number of running handles of 'a while ago'. It is possible that a
easy handle was removed in the meantime.

In order to check if that hypothesis is right, I moved the assertion
to directly below the call to curl_multi_socket_action where it
should hold. If this new assertion doesn't trigger than the hypothesis
was right and this is fixed.

indra/llmessage/aicurl.h

@@ -273,7 +273,7 @@ class AICurlEasyRequest {
 	// it's not thread-safe in itself.
 	AICurlEasyRequest(AICurlPrivate::BufferedCurlEasyRequestPtr const& ptr) : mBufferedCurlEasyRequest(ptr) { }
 
-	// This one is obviously dangerous. It's for use only in MultiHandle::check_run_count.
+	// This one is obviously dangerous. It's for use only in MultiHandle::check_msg_queue.
 	// See also the long comment in BufferedCurlEasyRequest::finalizeRequest with regard to CURLOPT_PRIVATE.
 	explicit AICurlEasyRequest(AICurlPrivate::ThreadSafeBufferedCurlEasyRequest* ptr) : mBufferedCurlEasyRequest(ptr) { }
 };