calcurse-caldav: replace readfp() by read_file()
calcurse-caldav: replace readfp() by read_file()

Addresses GitHub issue #209.

Signed-off-by: Lukas Fleischer <c9ca73f8336dcfb037ec2c2abf52d80a6847a5cd@calcurse.org>

lfos/calcurse,lfos/calcurse,lfos/calcurse