Various precision fixes for different machine precision.
This is in: verify_r1rho_kjaergaard_missing_r1
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 2014-08-28
Parent: [r25411]
Child: [r25413]
