New common unarchive code.

archival/libunarchive/data_extract_to_stdout.c

@@ -0,0 +1,8 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "unarchive.h"
+
+extern void data_extract_to_stdout(archive_handle_t *archive_handle)
+{
+	copy_file_chunk_fd(archive_handle->src_fd, fileno(stdout), archive_handle->file_header->size);
+}