in #using_task_library, only assume that +name+ is an orogen file if it ends in .orogen
in #using_task_library, only assume that +name+ is an orogen file if it ends in .orogen

This fixes a problem where

  using_task_library "bla"

would load the *file* bla if one is present in the current directory,
instead of loading the oroGen project called 'bla'.

doudou/modelkit-component,doudou/modelkit-component