Where is postgres.h in 7.1.3?

I am upgrading from 7.0.3 to 7.1.3.

canon=> select version ();
version
----------------------------------------------------------------------
PostgreSQL 7.1.3 on sparc-sun-solaris2.8, compiled by /opt/SUNWspro/bin/cc -Xa

I had created several compiled C functions, which now no longer work
because postgres.h does not appear to be part of the current distribution.

FWIW, the 7.1 docs at
(http://www7.us.postgresql.org/users-lounge/docs/7.1/programmer/xfunc-c.html)
section 13.4.1 (Base Types in C-Language functions) still contains the
sentence "Note that you should always include postgres.h first...", which
is exactly what I have done.

There is no mention of postgres.h being absent.

What gives?

Nishad
--
"Underneath the concrete, the dream is still alive" -- Talking Heads