teeinput

commented thms_unifying_with out; placed thm_db into signature again;
placed structures ThmDB and Readthy into Pure again;
changed init_thy_reader so that thm_db and loaded_thys are preserved
(necessary e.g. for ZF)

#! /bin/sh
#  teeinput -- start a program and log all inputs to a file
#     environment variable $LISTEN specifies the file name
tee -a -i $LISTEN | $*