into "gtk/column_prefs.c".
Get rid of "get_column_width()" - instead, export
"get_column_longest_string()", and have "get_column_width()"'s callers
make the GDK call to get the width of that string, so that "column.c"
contains no GTK+/GDK code.
svn path=/trunk/; revision=1447
Guy Harris