logic_compl:

Add neq_sym_equiv.

Binary_relation:
Modify {lex,colex}, *lex_nil, *lexF_irrefl (were *lex_irrefl),
       {lex,colex}F_conn_alt (were *lex_conn_alt).
Rename *lex_conn -> *lexF_conn.
Add *lex{F,T}, *lexT_{refl,antisym}.
WIP: {lex,colex}_trans, *lex_*order.

Monoid_compl:
WIP: section Lex_monomial_order_Facts1.
Modify gr*lex.