#5761 Inverse jacobi ns, nc, and nd functions are inaccurate or incorrect

[Raymond Toy]

As mentioned in https://sourceforge.net/p/maxima/bugs/5334/#3e4d, the other inverse Jacobi functions are inaccurate or incorrect. The inverse Jacobi sn, cn, and dn functions should produce correct results, so this is for the other inverse functions.

[Raymond Toy]

Fixed by merging branch bug-5761-inverse-jacobi-elliptics at commit [285b41]

See doc/info/impl-notes/inverse-jacobi-accuracy.texi.m4 for details on the changes.