usage:  int = quad2dc('Fun',xlow,xhigh,ylow,yhigh)
or
int = quad2dc('Fun',xlow,xhigh,ylow,yhigh,tol)

This function is similar to QUAD or QUAD8 for 2-dimensional integration,
but it uses a Gaussian-Chebyshev quadrature integration scheme.
int     -- value of the integral
Fun     -- Fun(x,y) (function to be integrated)
xlow    -- lower x limit of integration  (should be -xhigh)
xhigh   -- upper x limit of integration
ylow    -- lower y limit of integration  (should be -yhigh)
yhigh   -- upper y limit of integration
tol     -- tolerance parameter (optional)
The Gauss-Chebyshev Quadrature integrates an integral of the form
yhigh                xhigh
Int ((1/sqrt(1-y^2)) Int ((1/sqrt(1-x^2)) fun(x,y)) dx dy
-yhigh               -xlow