mail/gprof/tip: tap with the ugly stick

The ugly stick here is this bit in the respective headers:

#ifndef EXTERN
#define EXTERN extern
#endif

with a follow-up #define EXTERN in a single .c file to push all of their
definitions into one spot. A pass should be made over these three later to
push these definitions into the correct files instead, but this will suffice
for now and at a more leisurely pace.

MFC after: 3 days