revset: duplicate spanset.__contains__ to fullreposet for modification
1d7a2771aa36 says we should avoid function calls in __contains__, so
super(fullreposet, self).__contains__(rev) is not an option.
Actually the super call doubled the benchmark result of trivial query:
revisions:
0)
678f53865c68 (tip when I wrote this patch)
1) rev == node.nullrev or super(fullreposet, self).__contains__(rev)
revset #0: tip:0
0) wall 0.008441 comb 0.010000 user 0.010000 sys 0.000000 (best of 282)
1) wall 0.016152 comb 0.010000 user 0.010000 sys 0.000000 (best of 146)