* include/sane/sanei_config.h sanei/sanei_config.c: Add function
sanei_config_get_paths to obtain all configuration pathes (from env var
SANE_CONFIG_DIR and default paths); fix pointers to invalid/freed
strings when SANE_CONFIG_DIR is set
* backend/dll.c: When searching for the dll.d/ directory, also use
the SANE_CONFIG_DIR env variable.