When skipping input data, don't overflow a 32-bit size_t.

This can only happen on 32-bit systems when you're reading
an uncompressed archive and the skip request is an exact
multiple of 4G (e.g., skipping a tar entry with an 8G body).

The symptom is that the read_ahead() ends up returning zero
bytes, and the extraction stops with a premature end-of-file.

Using '1' here is more correct anyway, as it allows read_ahead()
to function opportunistically and minimize copying.

MFC after: 5 days

lib/libarchive/archive_read_support_compression_none.c

@@ -334,7 +334,7 @@ archive_decompressor_none_skip(struct archive_read *a, off_t request)
 		const void* dummy_buffer;
 		ssize_t bytes_read;
 		bytes_read = archive_decompressor_none_read_ahead(a,
-		    &dummy_buffer, request);
+		    &dummy_buffer, 1);
 		if (bytes_read < 0)
 			return (bytes_read);
 		if (bytes_read == 0) {