numeric slightly revised fdlibm

[David G Hough at validlab.com]

http://www.validlab.com/software/fdlibm.tar.gz

contains a slightly revised version of fdlibm.

e_pow.c and k_tan.c have been changed to correct a bug and to reduce
error bounds respectively.    Feel free to verify these in your own
diverse environments.

What has not changed is that certain improper uses of pointers cause bad
code to be generated by GCC with certain optimizations enabled.    So for
testing purposes, please compile unoptimized.

A version that is legitimate C is on my list of things to do.