Use of C99 extra long double math functions after r236148

[Stephen Montgomery-Smith]

Bruce, with both of us working at the same time on clog, it is getting 
hard for me to follow.  The version I sent this morning is the last 
change I made.

How about if you come the owner of the code for a while.  When you are 
finished, send it back to me, and I will look over everything you have 
done.  I won't work on it until then.  This works for me in other ways 
too, because my life is very busy at the moment.

If I do work on code, it will be on casinh/casin.  I am looking over the 
paper by Hull et al, and I am learning a lot from it.  One thing I did 
realize - casin and casinh are essentially the same.  If
#define reverse(z) cpack(cimag(z),creal(z))
then casin(z) = reverse(casinh(reverse(z))).  Unfortunately it is not so 
nice for cacos/cacosh.

I do like the progress we are making, and I appreciate your help very much.