explicit handling of ML environment within generic context;
eval_wrapper: non-critical, struct_name is always Isabelle, tuned comments;
eval_in/evaluate expect immutable Proof.context value;
use_text/use_file now depend on explicit ML name space;
#!/usr/bin/env bash
#
# $Id$
#
# psbooklet - rearrange pages of ps file to be printed as booklet (duplex)
#
psbook "$@" | \
pstops '4:0L@.7(21cm,0cm)+1L@.7(21cm,14.85cm),3R@.7(0cm,14.85cm)+2R@.7(0cm,29.7cm)'