fixed explosion when computing accessibility

use "eproof_ram" script if available (plug-in replacement for "eproof", but faster)

tuning

merged

further imitation of "usedir" shell script; Pure/build observes build_images option, unlike traditional version; tuned signature;

make nat_cancel_sums simprocs robust in the presence of schematic variables; add regression tests

export code relatively to master directory

require explicit initialization of options; more explicit Position operations;

tuned signature;

define build_options from command line;

some basic Isabelle options;

basic jEdit mode for Isabelle options;

basic support for stand-alone options with external string representation;

minimal build_job;

restrict to required sessions;

proper commas_quote;

tune;

simplified script to build Isabelle/ML;

added eq_file / copy_file corresponding to File.eq / File.copy in ML;

merged

removed ML module DSeq which was a part of the ancient code generator (cf. 58e33a125f32)

deactivating quickcheck narrowing examples to find out if this causes the system error on the current isatest

support for detached Bash_Job with some control operations;

allow catalog entries to be commented-out;

support external processes with explicit environment;

include COMPONENT/etc/sessions as catalog for more directories, for improved scalability with hundreds of entries (notably AFP); misc tuning and simplification;

less redundant data structures;

clarified topological ordering: preserve order of adjacency via reverse fold;

support Session.Queue with ordering and dependencies;

clarified signature;