A sequence of changes where system is melted several times, with
varying versions of a routine (external, deferred, once) moved back
and forth between two classes and with several errors along the way
(VXRC, VDRD(7), VMFN, EXT_SAME_SIGN) causes the compiler to die with a
segmentation fault in `set_has_loop'.

Discovered in Release 5.0.015.