[fit_out,x,err] =
FitGammaWeib(values_in,measurements,values_out,x0)
Fits a Weibull function to the passed gamma data.
10/3/93 dhb Created from jms code to fit psychometric functions
3/4/05 dhb Conditionals for optimization toolbox version.
dhb Encapsulate error calculation
Psychtoolbox/PsychGamma/FitGammaWeib.m