This allows the suppressMessages to work on print functions. This captures the output via R.Util's captureOutput function and then sends it through the message routine.
nlmixrPrint(x, ...)object to print
Other things output
catpureOutput was used since it is much faster than the internal capture.output see https://www.r-bloggers.com/performance-captureoutput-is-much-faster-than-capture-output/