Test mpfr special functions
---------------------------

    >>> import gmpy2
    >>> from gmpy2 import mpfr

Test agm
--------

Test ai
-------

Test const_catalan
------------------

Test const_euler
----------------

Test const_log2
---------------

Test const_pi
-------------

Test digamma
------------

Test eint
---------

Test erf
--------

Test erfc
---------

Test factorial
--------------

Test f2q
--------

Test fma
--------

Test fmod
---------

Test fms
--------

Test frac
---------

Test frexp
----------

Test fsum
---------

Test gamma
----------

Test j0
-------

Test j1
-------

Test jn
-------

Test lgamma
-----------

Test li2
--------

Test lngamma
------------

Test modf
---------

Test mul_2exp
-------------

Test next_above
---------------

Test next_below
---------------

Test next_toward
----------------

Test rec_sqrt
-------------

Test reldiff
------------

Test remainder
--------------

Test remquo
-----------

Test root
---------

Test sqrt
---------

Test y0
-------

Test y1
-------

Test yn
-------

Test zeta
---------