rtl_test: refactoring and optimization for PPM error

Signed-off-by: Steve Markgraf <steve@steve-m.de>
rtl_sdr: clean up getopt-string

Signed-off-by: Steve Markgraf <steve@steve-m.de>
rtl_test: update copyright header

Signed-off-by: Steve Markgraf <steve@steve-m.de>