Moved the argument 'chi2_jacobian' as the last argument in estimate_r2eff_err.
This argument is highly likely not to be used, but is kept for future testing purposes.
task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.
Authored by: tlinnet 2014-08-29
Parent: [r25467]
Child: [r25469]
