Changes since 1.62
1. JDMread_i_int16, etc added.

Changes since 1.61
1. JDMfinite returns 1 if OS does not support finite function.

Changes since 1.40

1. JDMc_sqrt tweaked to return a value consistent with the branch cut
   defined by FORTRAN.

2. Added Mark Olesen's version of Singleton's mixed-radix fft.  See
   src/fftn.c.

