Add FILLELLIPSE to graphics functions

[hjellinek]

As I was building a test suite for Issue #1814, I noticed a minor incongruity.

Medley includes functions DRAWPOLYGON and DRAWCIRCLE, and corresponding functions FILLPOLYGON and FILLCIRCLE. But DRAWELLIPSE, cousin of DRAWCIRCLE, lacks a corresponding FILLELLIPSE function.

This would require us to add an IMFILLELLIPSE slot to IMAGEOPS with a suitable (no-op) default value.

[nbriggs]

A quick survey suggests that the following would likely need to be recompiled because they depend on the definition of the IMAGEOPS record (which lives in IMAGEIO), does that seem right to you?

library/BIGBITMAPS
library/FX-80DRIVER
library/POSTSCRIPTSTREAM
library/PRESS
library/sketch/SKETCH-BMELT
library/sketch/SKETCH-ELEMENTS
library/sketch/SKETCH-STREAM
library/tedit/TEDIT-STREAM
lispusers/CHATSERVER
lispusers/COURIERIMAGESTREAM
lispusers/DSPSCALE
lispusers/HPGL
lispusers/PS-SKETCH-PATCH
sources/APRINT
sources/FILEIO
sources/FONT
sources/HARDCOPY
sources/IMAGEIO
sources/INTERPRESS
sources/LLDISPLAY
sources/WINDOW

[hjellinek]

Yes, at least those.