Add a new routine to create the ".ethereal" directory for a user.

Add a new routine to create the ".ethereal" directory for a user.

Use that routine rather than duplicating that code in the routines to
write out the preference file and filter files.

Use it in the code for the color filter dialog, so that the directory in
question is created if necessary.

As that routine returns an error indication, have the code that calls
that routine put up a message box if the attempt fails.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@4065 f5534014-38df-0310-8fa8-9805f1628bb7