Let message field and button bar use GTK -messageFont

Let message field and button bar use GTK -messageFont

The -messageFont spec (using the default coordFont pixel size, like the
others) is now used to modify the fonts of message field and buttons
in the button bar. They pass a pointer to the appData font variable in
their Option's textField. This conflicts with the use of this field in
buttons for specifying a color, as done in the New Variant buttons.
This is resolved by checking if the first byte of the pointed-to value
is a #. The Xaw version must ignore the textField if it does not
specify a color.