DecoderBuffer: remove unused method _is_empty()

src/decoder/DecoderBuffer.cxx

@@ -76,12 +76,6 @@ decoder_buffer_get_stream(const DecoderBuffer *buffer)
 }
 
 bool
-decoder_buffer_is_empty(const DecoderBuffer *buffer)
-{
-	return buffer->consumed == buffer->length;
-}
-
-bool
 decoder_buffer_is_full(const DecoderBuffer *buffer)
 {
 	return buffer->consumed == 0 && buffer->length == buffer->size;

src/decoder/DecoderBuffer.hxx

@@ -60,10 +60,6 @@ decoder_buffer_get_stream(const DecoderBuffer *buffer);
 
 gcc_pure
 bool
-decoder_buffer_is_empty(const DecoderBuffer *buffer);
-
-gcc_pure
-bool
 decoder_buffer_is_full(const DecoderBuffer *buffer);
 
 void