Use of C99 extra long double math functions after r236148

[Stephen Montgomery-Smith]

I am committing the software - as is - to you guys.

I feel that I worked extremely hard to get an error less than about 3.8 
ULP (from 10,000,000 test cases) for the complex arc-trig and 
arc-hyperbolic functions.  My skill is writing numerical software that 
works, with an awareness of where various numerical issues might arise. 
  I am very proud of the work I have done in the last few days.

Now this software requires a different skill set, getting it to conform 
to various styles, looking for smart efficiencies to overcome defects in 
the compiler, and checking that NaN's work properly.  This is a skill 
set which you guys have in far greater amounts than I have.  And it is 
something that doesn't engage my interest.

If you find problems, like unwanted overflows/underflows or numerical 
errors occurring in edge cases, then by all means get back to me, and I 
will attempt to fix it.

Thus far, the only fault I have found so far is in catanh, where I 
forgot to set the "inexact flag" when computing "hp" and "hm" when |y| 
is very small.

I will still continue working hard on getting the numerics in clog to 
work correctly.

Stephen