#1 block bug

[Lionel Thiry]

Quick exposition of the bug:

What I have done with R-sharp:
>> a: [one twoo]
== [one twoo]
>> next a
== [twoo]
>> a
== [twoo]
>> back a
== [one twoo]
>> b: next a
== [twoo]
>> a
== [twoo]
>> b
== [twoo]
>> index? a
== 2
>> index? b
== 2

What it gives with rebol:
>> a: [one twoo]
== [one twoo]
>> next a
== [twoo]
>> a
== [one twoo]
>> b: next a
== [twoo]
>> a
== [one twoo]
>> b
== [twoo]
>> index? a
== 1
>> index? b
== 2

In fact, in rebol, most block mecanisms work as if it
was in a functionnal way. But a and b still refer to
the same block, There is juste a difference in the index.

Lio