Fix bug #3191: parsing problem: thru 3 for i in [a,b]

Fix bug #3191: parsing problem: thru 3 for i in [a,b]

This would cause a parse error:

(%i1) for i in [1, 2, 3, 4] thru 3 do print (i)$
incorrect syntax: A do cannot have a thru with a in field.
n [1, 2, 3, 4] thru
                  ^

But this rearranged expression would not:

(%i1) thru 3 for i in [1, 2, 3, 4] do print (i)$
1
2
3

Now these both cause parse errors.

No problems with the test suite, share test suite or rtest_translator.
New tests have been added to rtest1.