added turkanis as maintianer of rational

[SVN r29419]

libs/maintainers.txt

@@ -40,7 +40,7 @@ ptr_container         Thorsten Ottosen <nesotto -at- cs.auc.dk>
 python                David Abrahams <dave -at- boost-consulting.com>
 random
 range                 Thorsten Ottosen <nesotto -at- cs.auc.dk>
-rational
+rational              Jonathan Turkanis <technews -at- kangaroologic.com>
 regex                 John Maddock <john -at- johnmaddock.co.uk>
 serialization         Robert Ramey <ramey -at- rrsd.com>
 signals               Douglas Gregor <dgregor -at- cs.indiana.edu>