added aclent_t autoconf test (defines as an int if it doesn't exist).

added aclent_t autoconf test (defines as an int if it doesn't exist).
this is to stop a compilation error caused by make proto putting
functions that are wrapped in #if HAVE_ACLxxx code.

maybe a better fix would be to have mkproto.awk exclude any functions
wrapped in #if HAVEs that don't exist.
(This used to be commit 361c1b7ea994cc25d460ebd25b2ad9025f90848c)