Prefs Window: Added missing application icon.
Pixmaps: Cleaned up the Ekiga icon.
Powermeter: Dropped useless code & pixmaps.
Pixmaps: More cleanups.

Unused files were removed. Used files were converted into "theme" icons.
Useless gmstockicons.h file has been removed.
Pixmaps: More cleanups. Added new scalable icon thanks to Jimmac.
MLogo: Added parameter to prevent the logo to move.

Displaying a moving logo when there is no videoinput is a rather bad
idea. We consume bandwidth for nothing. The default image to display is
"hardcoded". Further developments will allow to stream the user avatar
when there is no video at all.
Pixmaps: Added no video icon (png version).
CodecsBox: Removed deprecated stuff.
Engine: Take autoconf DEBUG into account.

This was hardcoded in the files. It is useless as we have an autoconf
parameter.
ChatArea: Removed deprecated GTK+3 functions.
MenuBuilderGtk: Removed deprecated GTK+3 functions.
CallWindow: Destroy CallWindow one time only.

This is enough ;)
Pixmaps: Fixed YUV icon generation.
TODO: More to do...