MEDIUM: ssl: crt-base and key-base local keywords for crt-store

MEDIUM: ssl: crt-base and key-base local keywords for crt-store

Add support for crt-base and key-base local keywords for the crt-store.

current_crtbase and current_keybase are filed with a copy of the global
keyword argument when a crt-store is declared, and updated with a new
path when the keywords are in the crt-store section.

The ckch_conf_kws[] array was updated with &current_crtbase and
&current_keybase instead of the global_ssl ones so the parser can use
them.

The keyword must be used before any "load" line in a crt-store section.

Example:

    crt-store web
        crt-base /etc/ssl/certs/
        key-base /etc/ssl/private/
        load crt "site3.crt" alias "site3"
        load crt "site4.crt" key "site4.key"

    frontend in2
        bind *:443 ssl crt "@web/site3" crt "@web/site4.crt"