'b.sh' is the source for the shell command file 'b',
the entry point for the user into the B system.
It will be installed in ../../bin, or in the
public place defined in the root Makefile.

All other files are auxiliary files for 'b', and will
be installed in ../../lib, or in the library
destination defined in the root Makefile.

The b.sh and b_p.sh shell scripts are modified by make;
because some tar's leave the owner of the tape as the owner
of the extracted files we make sure that ../../Setup creates
writable versions from the *.gen files.