improve speed of wdba-minimization
Here is a formula (reported by Étienne Renault) where WDBA-minimization takes a lot time, yet it is useless!
% f='(Fa U (Fb xor ((c xor Fd) W e))) U Gf'
% ltl2tgba -x wdba-minimize=0 "$f" --stats '%s states, %r seconds'
81 states, 0.377423 seconds
% ltl2tgba -x wdba-minimize=1 "$f" --stats '%s states, %r seconds'
81 states, 41.5798 seconds