Adapted sipsimple.session to use RouteHeader instead of Route

Ignore-this: 479d3142129115cfc130e36c932b631e

darcs-hash:20090624110226-1e3d8-69523edf9f6d5fa6bfff802f5e3bb22a21817891
Adapted sipsimple.session2 to use RouteHeader instead of Route

Ignore-this: b144222f652223c685937e5aa55de7f0

darcs-hash:20090624110236-1e3d8-0731e853574803a549f9d695d64af8afb335c8dc