[krbdev.mit.edu #1364] make depend requires use of Gnu sed under Irix

[Ken Raeburn via RT]

Actually, it seems to be the "s///p" form (print *if* a substitution was
done) that IRIX sed is treating differently, and only when it's followed
by more modifications to the pattern space, printing, etc.  I believe
the substitutions are arranged to always be performed, so using a
separate print command seems to be a reasonable change, and it gets me
the same results using IRIX and GNU sed.