idl vs. gdl difference in foreach behaviour

[slayoo]

(moved from https://sourceforge.net/p/gnudatalanguage/bugs/630/)
As reported on SF:

GDL> a = [1,2,3]
GDL> foreach a, a do print, a
1
2
3
GDL>

IDL> a = [1,2,3]
IDL> foreach a, a do print, a
1
IDL>

[GillesDuvert]

#1786 introduced this case in test_foreach, but I removed the test as there is no possibility I could make FOREACH behave like IDL in this particular case without endangering all FOREACHs other cases. Best left open and unsolved.