libpayload: Implement strlcpy

Change-Id: Ibd339957690afe2cded46895c3088eba87f0ffd1
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/85
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
3 files changed