Mark (elem) and (cont) iffy -- also make (cont) an only instead of a …

…multi.

lib/CORE.setting

@@ -2040,13 +2040,13 @@ constant term:<∅> = set();
 proto sub infix:<∈>($, $ --> Bool) is equiv(&infix:<==>) {*}
 multi sub infix:<∈>($a, Any $b --> Bool) { $a ∈ Set($b) }
 multi sub infix:<∈>($a, Set $b --> Bool) { $b.exists($a) }
-only  sub infix:<(elem)>($a, $b --> Bool) { $a ∈ $b }
+only  sub infix:<(elem)>($a, $b --> Bool) is iffy { $a ∈ $b }
 only  sub infix:<∉>($a, $b --> Bool) is equiv(&infix:<==>) { $a !∈ $b }
 
 proto sub infix:<∋>($, $ --> Bool) is equiv(&infix:<==>) {*}
 multi sub infix:<∋>(Any $a, $b --> Bool) { Set($a) ∋ $b }
 multi sub infix:<∋>(Set $a, $b --> Bool) { $a.exists($b) }
-multi sub infix:<(cont)>($a, $b --> Bool) { $a ∋ $b }
+only  sub infix:<(cont)>($a, $b --> Bool) is iffy { $a ∋ $b }
 only  sub infix:<∌>($a, $b --> Bool) is equiv(&infix:<==>) { $a !∋ $b }
 
 proto sub infix:<∪>($, $ --> Set) is equiv(&infix:<X>) {*}