Tabling: another core dump

With latest git (8.1.8-25-g583b8636c):

103 ?- time(i0_i_maxSteps0_maxSteps(1, 1 000 000, 0, R)).
% 72,659,302 inferences, 12.005 CPU in 12.061 seconds (100% CPU, 6052541 Lips)
R = 524.

104 ?- time(i0_i_maxSteps0_maxSteps(1, 1 000 000, 0, R)).
% 5,000,001 inferences, 1.165 CPU in 1.169 seconds (100% CPU, 4290451 Lips)
R = 524.

These patches also fix Tabling: Core dump