ggGetUserDir - Get user home directory
const char * ggGetUserDir(void);
ggGetUserDir returns a path to the home directory of the user executing
an application, whatever it may be on a given system. For example, on
unix systems it will be the contents of the HOME environment variable.
If no user home exists, a suitable temporary directory is found.
ggGetUserDir is threadsafe, but is not guaranteed to be safe to use in
a thread that may be cancelled during its execution. It is also not
guaranteed to be safe to use in special contexts such as LibGG task
handlers, signal handlers and asyncronous procedure calls.
ggGetUserDir returns a NULL-terminated string holding the path the the
current user home directory. This string may be a reference to memory
belonging to OS facilities, and *must not* be freed or altered.