rename archival/libunarchive -> archival/libarchive; move bz/ into it

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/libarchive/seek_by_jump.c b/archival/libarchive/seek_by_jump.c
new file mode 100644
index 0000000..7c2c52a
--- /dev/null
+++ b/archival/libarchive/seek_by_jump.c
@@ -0,0 +1,19 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+#include "libbb.h"
+#include "archive.h"
+
+void FAST_FUNC seek_by_jump(int fd, off_t amount)
+{
+	if (amount
+	 && lseek(fd, amount, SEEK_CUR) == (off_t) -1
+	) {
+		if (errno == ESPIPE)
+			seek_by_read(fd, amount);
+		else
+			bb_perror_msg_and_die("seek failure");
+	}
+}