Fix missing files in tar generation, by using a tar format that doesn't have short limits on file name lengths. (and that is still readable by the Python tarfile module)

[SVN r39616]

tools/regression/boost_svn_export_archive.sh

@@ -34,7 +34,7 @@ make_archive()
 {
   svn_export \
     | cut --bytes=6- \
-    | star -c -D -to-stdout -d artype=tar list=- 2>/dev/null \
+    | star -c -D -to-stdout -d artype=pax list=- 2>/dev/null \
     | bzip2 -6 -c \
     | tee $1 \
     | tar -jtf - \