Description of problem:

Sometimes Wesnoth runs just fine in windowed mode, however sometimes the size of
the Wesnoth window and the Wesnoth game resolution are not the same and SDL
scaling happens.

When that happens, the CPU use of my X server goes over 90% and still the screen
only updates two or three times a second.  Totally unplayable :(

Version-Release number of selected component (if applicable):

wesnoth-1.0.2-3.fc6

Steps to Reproduce:
1. play wesnoth in windowed mode
2. resize the window
3. suffer
  
Expected results:

Wesnoth should either refuse to have its window resized to unplayable
resolutions, or it should make sure the image is scaled in a faster way.

Additional info:

1) I do NOT resize the window myself.  Wesnoth for some reason starts up with
the window the wrong size.  I even removed the window resolution bits from the
configuration file to try and fix things, and it STILL picked the wrong resolution!

2) due to my Xinerama (well, Radeon mergedfb) setup, I cannot play wesnoth full
screen

3) maybe wesnoth should not allow scaling the window to "bad" resolutions?