[Boost-build] Alias rule related documentation patch.

From: Jurko Gospodnetiæ (jurko.gospodnetic_at_[hidden])
Date: 2007-12-22 23:02:51

   Hi.

   Attached patch corrects an invalid example and does some minor 
stylistic changes in the alias rule documentation.

   Hope this helps.

   Best regards,
     Jurko Gospodnetiæ