* Makes submenu indicator arrows point in the direction that the submenu
will pop up (left or right), rather than always right.
* Makes the submenu offset (the vertical offset of each sucessive submenu)
a #define'd quantity, instead of magic in the middle.
Someone should make this be user-customizable via .gtkrc etc.
* Removes hard-coding of submenus cascade right, and #define's it.
This should also be user settable (i18n issues? tfel-ot-thgir languages
probably should default to cascade left).
* Minor code clean up (moved an assignment that sometimes gets immediately
by an 'if ...' into the 'else').
