Update libtool.

Monotone-Parent: 25998a2c4e61d05a1cc394f7a6a4cf4482b99f21
Monotone-Revision: 3f657a9069149f9fb9ba691acd05d8f4028aa600
Update ltmain.sh.

Monotone-Parent: 3f657a9069149f9fb9ba691acd05d8f4028aa600
Monotone-Revision: 39e57bc064c422c9465ed9a3febfe87d7e6654d8