input/async: use class HugeArray instead of HugeAllocation

src/input/AsyncInputStream.cxx

@@ -37,7 +37,7 @@ AsyncInputStream::AsyncInputStream(EventLoop &event_loop, const char *_url,
 	 deferred_resume(event_loop, BIND_THIS_METHOD(DeferredResume)),
 	 deferred_seek(event_loop, BIND_THIS_METHOD(DeferredSeek)),
 	 allocation(_buffer_size),
-	 buffer((uint8_t *)allocation.get(), _buffer_size),
+	 buffer(&allocation.front(), allocation.size()),
 	 resume_at(_resume_at)
 {
 	allocation.ForkCow(false);

src/input/AsyncInputStream.hxx

@@ -41,7 +41,7 @@ class AsyncInputStream : public InputStream {
 	DeferredCall deferred_resume;
 	DeferredCall deferred_seek;
 
-	HugeAllocation allocation;
+	HugeArray<uint8_t> allocation;
 
 	CircularBuffer<uint8_t> buffer;
 	const size_t resume_at;