Revision 121

In procedure fxhyp, extracted the body of the loop on ik into a new
procedure:  fxhyp_loop_ik.

dzoomx and dzoomy must now be fractions of the entire range, they
cannot be ranges in degrees or rad.

In fxhyp, force Xf(2 * nmax) = pi_d instead of possibly doing it in
fxhyp_loop_ik.

In fxhyp_loop_ik, when testing whether xvrai is between -pi and pi,
changed the boundaries from -pi - 0.1 to - pi_d - 1d-5 and from pi +
0.1 to pi_d + 1d-5. This reveals a misconception of the
code. Therefore, this version does not work.