- use PATH_SEPARATOR everywhere,
instead of a mix of PATH_SEPARATOR and hard coded colons.
- always include /usr/share/yubikey-val first,
then /etc/yubico/val.
- should not have any visible affects,
since no file names are common between the two directories.
- use array+implode to make it easier to add/remove paths,
and to avoid hardcoded the path separator.
- don't depend on external binaries,
it assumes too much and is dangerous.
- we can depend on libcurl instead,
since it's already a dependency in core.
- we should do this for other plugins too,
and move the new function into ykval-common.php
- plugin reports same exact values as before.
