incorrect inline docs for `eos_poly_piece::csnd_from_gm1`

[rhaas80]

The current (e59d68d) RePrimAnd code for real_t eos_poly_piece::csnd_from_gm1(real_t gm1) const reads:

/**
\return Soundspeed squared \f$ c_s^2 = \frac{g-1-\delta\epsilon}{ng} \f$
*/
real_t eos_poly_piece::csnd_from_gm1(real_t gm1) const
{
  real_t gm1p  = gm1 - dsed;
  return sqrt(gm1p / ( n * (gm1 + 1.0)));
}

so claims to compute "Soundspeed squared" but actually computes sound speed (not squared) as the name would indicate.

[wokast]

Indeed, the function returns the unsquared soundspeed as it is supposed to do. The documentation is wrong. Will be fixed in next service release.