Use of C99 extra long double math functions after r236148

[Stephen Montgomery-Smith]

I am not getting many responses to the programs I submitted.  I 
understand that you may be all very busy.  The casinh algorithm in 
particular will take a lot of vetting.  So I have submitted them in a PR 
so that they won't get lost.

http://www.freebsd.org/cgi/query-pr.cgi?pr=170206

The only substantive changes I made was (1) make corrections in comments 
for catanh and (2) implement clogf by calling clog.  (Unsurprisingly its 
relative error is less than or equal to 0.5 ULP.)

If I used the incorrect category (I used bin), please tell me or change 
it for me.

Thanks, Stephen