Using Expect 5.38.0 and Tcl/Tk 8.4.1 on a 64-bit HPUX
11.00 machine the linking stage of building fails with
an undefined reference to matherr error in
exp_main_tk.c. I discovered that the reference to
matherr only needs to be used on the Sun platform, so I
wrapped an #ifdef around the reference that should only
be true on the machines that need to use matherr.