Segmentation Fault in guile-1.8.7 on recent Macbook Pro

[Fabian Schuetz]

While experimenting with "undefine", I discovered, that 
even quite important functions, like "write" or "display"
can be undefined. The problem is, that calling them
after they have been "undefined", leads to an 
endless regression, displaying a Segmentation fault,
when finally interrupted. 

If I "undefine" list:
(undefine list)
and call it afterwards:
(list 1 2 3 4)
I get the expected "ABORT: (unbound-variable)

I would be glad to help out, to fix this.

Be greeted,
Fabian Schütz