loadable builtins on HP-UX

[Greg Wooledge]

To the surprise of approximately zero people, loadable builtins don't
fully work on HP-UX.

I'll spare you any results from 10.20 because it's totally unsupported
at this point.  (It doesn't even use dlopen().)

On HP-UX 11.11, things half work.  This is with 4.4-beta, sitting in the
.../examples/loadables/ directory, after a "make all":

bash-4.4# enable -f ./finfo finfo
bash: enable: cannot find finfo_struct in shared object ./finfo: Unresolved 
module for symbol: sh_optarg (data)  from ./finfo

bash-4.4# enable -f ./tty tty
bash-4.4# type -a tty
tty is a shell builtin
tty is /usr/bin/tty
bash-4.4# tty
/usr/lib/dld.sl: Unresolved symbol: reset_internal_getopt (code)  from ./tty
/usr/lib/dld.sl: Unresolved symbol: reset_internal_getopt (code)  from ./tty
ABORT instruction (core dumped)