[krbdev.mit.edu #6721] Compilation fails with -DDEBUG

[Russ Allbery <rra@stanford.edu> via RT]

I needed to build the current tree with -DDEBUG to debug a PKINIT issue
and discovered when doing so that the kadmin code doesn't build with
-DDEBUG.  It defines a debugging macro to xprintf, which is not defined
anywhere in the tree.