Package initialization made possible when executed in environments whithout access to the home directory.

Functions _get_xdg_config_dir(), _get_xdg_cache_dir(), _get_config_or_cache_dir() allow now the use of the environment variables XDG_CONFIG_HOME resp. XDG_CACHE_HOME without requiring access to the home directory (f.ex. in batch jobs on clusters).

Before, the definitions of the environment variables would not have been used when the home directory was not accessible. Nevertheless, the standard does not bind the variable definitions to the existence of home directories (only the default values are defined with respect to them).
Merge pull request #2719 from michs/xdg_home-config

Package initialization made possible when executed in environments with...