FIXED: variant_sha1/2 for indirect datatypes (big ints, strings, floats).
Samer Abdallah.
ADDED: library(sandbox): allow using :- op/3 in directives, provided the
declaration is not qualified.
Updated pengines
Updated http
Updated pengines
Preparing version 7.1.22
document the need for a more general mechanism for attributed variables
Merge branch 'master' into sandbox
add further safe predicates to library(sandbox) for compatibility with existing code

Potentially missing 0-ary predicates found with:

   run :-
           current_predicate(P),
           P = F/0,
           catch((safe_goal(F), Safe = true), _, Safe = false),
           \+ Safe,
           writeln(P),
           false.

Query:

     ?- run.
     run/0
     halt/0
     $pop_input_context/0
     $query_loop/0
     attach_packs/0
     abort/0
     $qlf_close/0
     reset_profiler/0
     $new_findall_bag/0
     $make_system_source_files/0
     reload_library_index/0
     $compile_wic/0
     ttyflush/0
     prolog/0
     mutex_statistics/0
     $close_wic/0
     $compile/0
     at_end_of_stream/0
     $destroy_findall_bag/0
     $run_at_halt/0
     $suspend_findall_bag/0
     $fail/0
     noprotocol/0
     trim_stacks/0
     notrace/0
     shell/0
     $toplevel/0
     trace/0
     break/0
     seen/0
     $load_additional_boot_files/0
     tracing/0
     $initialise/0
     $thread_init/0
     mutex_unlock_all/0
     told/0
     debugging/0
     $trap_gdb/0
     $update_library_index/0
     $qlf_end_part/0
     nospyall/0

ttyflush/0 still pending.