[krbdev.mit.edu #2786] dead code in init_common() causes malloc(0)

[Ken Raeburn]

I don't think the code is doing anything actually invalid according to 
the C-1990 spec (which we're assuming compliance to).  It allows 
malloc(0) calls (returning either NULL or a unique pointer), and memcpy 
shouldn't be reading or storing anything if the length is zero.

Nevertheless, if it's always a null pointer and zero length, it is kind 
of silly for us to have those calls there.

Ken