Computes the condition number of the pow function.
[c,y] = condnb_powcond ( x , a )
a n-by-m matrix of doubles
a n-by-m matrix of doubles
a n-by-m matrix of doubles, the condition number
a n-by-m, matrix of doubles, the function values
Computes the condition number of the pow function. The pow function has a large condition number if a is large.