Import global WP function

[szepeviktor]

e.g. in CachePool

use function set_transient;
use function delete_transient;
use function get_transient;
use function get_option;

What do you think about it?

[XedinUnknown]

Function import is a good way to disambiguate function names, and make it obvious from the start what is being used throughout the file.

If you would like to do this, I'd welcome a PR :)

[szepeviktor]

Done.