[Cfp-interest 1905] cr_xxx functions

[Paul Zimmermann]

       Hi,

I just checked the reserved names for correctly rounded functions in N2596
(http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2596.pdf) page 392.
I have a few comments:

* why is cr_acosh before cr_acos? I would put cr_acos before cr_acosh and cr_acospi.

* the cr_sqrt function is missing

* are also missing: cr_cbrt, cr_erf, cr_erfc, cr_j0, cr_lgamma, cr_tgamma
  (the Bessel functions j0, j1, jn, y0, y1, yn are not in the C standard,
  thus it makes sense that the cr_xxx variants are not reserved)

Best regards,
Paul