krb4 library major version bump

[Sam Hartman]

We seem to have changed the ABI on Unix for krb4 in that I seem to get
strange failures using applications linked against 1.2.x with -current
shared libraries.  This is not surprising, but we should make sure that:

1) We consider this acceptable

2) We know at least one change that should create ABI divergence 

3) We are willing to accept a so bump for the krb4 libs.