Skolemizing not handled correctly

[grayswandyr]

          Recall Skolemizing too: this won't compile with Electrod

sig S { var r : set S}
run { some s : set S | some s } for 3 Int

fails.
Electrod:

electrod (C) 2016-2020 ONERA 1.0.0-1-geb0b02e
[E002] 00000.elo:23.13-23.20: syntax error this##S
       (some s: set this##S { 
Aborting (1.973ms).

Originally posted by @grayswandyr in AlloyTools/org.alloytools.alloy#197 (comment)

[grayswandyr]

Note: the previous description concerns "first-order" Skolemization, which fails at the electrod level.
"Higher-order" Skolemization is OTOH intercepted at the Alloy level and not even passed to electrod:

[grayswandyr]

In:

sig S { var r : set S}
run { some s : MULT S | some s } for 3 Int

MULT can be: set, some, one, lone but also seq (which stands for seq/Int -> S in this case).

[grayswandyr]

Handled in Pardinus itself.