Log Message:
Update to 0.13:

     o   All Buildtool control files (the ones in the buildtool.d subdirecto-
         ry) were unified into a single file, Generic.bt, which is placed in
         the top level directory for simplicity.  Everything is now controlled
         from shell functions defined in that file.  Buildtool will assist you
         in this conversion when needed.

     o   The bt_sh module was added, a very fast and small shell interpreter.

     o   The bt_logic module was extended (really, rewritten from scratch) to
         provide a shell based program to track dependancies and build tar-
         gets.  It still acts as a wrapper for compilation and linking com-
         mands.  As a side effect, the old code was readded as the bt_wrap
         module, needed to keep bt_make working until both can be safely re-
         moved.

     o   bt_config will now check for several programs to generate dependancy
         files.  Aside from the standard cpp(1), it also searches for fastdep,
         which will give better results on slow computers.

     o   Some bug fixes.