*: make GNU licensing statement forms more regular

This change retains "or later" state! No licensing _changes_ here,
only form is adjusted (article, space between "GPL" and "v2" and so on).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/libunarchive/decompress_bunzip2.c b/archival/libunarchive/decompress_bunzip2.c
index bdbd39a..2201568 100644
--- a/archival/libunarchive/decompress_bunzip2.c
+++ b/archival/libunarchive/decompress_bunzip2.c
@@ -6,7 +6,7 @@
    Peter Fenwick, Alistair Moffat, Radford Neal, Ian H. Witten,
    Robert Sedgewick, and Jon L. Bentley.
 
-   Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+   Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
 
 /*