[Bug-gsl] gsl_sf_ellint_Kcomp stalls on GSL_NAN

[Victor Zverovich]

Running

    gsl_sf_ellint_Kcomp(GSL_NAN, GSL_PREC_DOUBLE);

stalls on EPEL6 instead of giving an error as it does on some other systems
(like Ubuntu 16.04 with gcc 5.3.1):

  .../ellint.c:225: ERROR: too many iterations error
  Default GSL error handler invoked.

This issue has initially been reported here:
https://github.com/ampl/mp/issues/103.

Version of GSL used: 2.1

Thanks,
Victor