BATs are built automatically now.

* BATs generate a *.h and a *.c file
* Each BAT is a single *.so
* Clauses are now obtained with init_bat() instead of the
  DECL_ALL_CLAUSES macro
* In ECLiPSe-CLP, one shall first load the BAT's *.so, then the
  ec_interface.so, and then use the external holds/1 predicate;
  an interface to init_bat() is coming up