- Introduced posix_errno() (get error number from last error message) and

- Introduced posix_errno() (get error number from last error message) and
  posix_strerror() (convert error number into error string).

- Do not output any error message if any of the function fails with FALSE
  return value. The proper way now is to call posix_errno() and
  posix_strerror() after encountering an error condition.

- Function not support on a system no longer issue a 'not available' error
  but simply don't exist so we can safely use 'function_exists'.

- Fixed protos.

- Use new parameter parsing API.

- posix_uname() may be aware of 'domainname' (GNU extension)

- posix_getgrnam(), posix_getgrgid(): the returned information does no
  longer contains mixture of string and numbered keys (hash / array)
  but contains key 'member' with an array of all members in a list
  (or an empty array). This breaks BC but is the right thing IMHO.