MINOR: ssl: handle PARSE_TYPE_INT and PARSE_TYPE_ONOFF in ckch_store_load_files()

MINOR: ssl: handle PARSE_TYPE_INT and PARSE_TYPE_ONOFF in ckch_store_load_files()

The callback used by ckch_store_load_files() only works with
PARSE_TYPE_STR.

This allows to use a callback which will use a integer type for PARSE_TYPE_INT
and PARSE_TYPE_ONOFF.

This require to change the type of the callback to void * to pass either
a char * or a int depending of the parsing type.

The ssl_sock_load_* functions were encapsuled in ckch_conf_load_*
function just to match the type.

This will allow to handle crt-store keywords that are ONOFF or INT
types.