[Gtkradiant] Crash fix patches for trunk

[Timothee Besset]

> Nerius Landys wrote:

[..]

>>
>> What other tools/functions are broken when you use uppercase letters
>> in resource names?  I'm kind of curious.
>>
> 
> Shader parsing I believe, finding the stage images etc., same for model
> skins, etc.
> 
> It's really better to ask people to have a good policy of sticking to
> lowercase than hoping you'll be patching case support forever.
> 

Also a lot of those problems are in the engine itself. It may be ok if
it's an open sourced one, but RTCW, Wolf:ET and QuakeLive are not.

TTimo