fix warnings related to multiple include of the same header file

[RenaudFondeur]

small change to fix the 'warning, attempt to include <sys/stat.h> / for e.g. mkdir / a second time' happening in Slang during C code generation.

the class AbstractImageAccess include sys/stat.h and the subclasses don't override declareCVarsIn: so we get the warning for each of them each time a CCodeGenerator is created.

[guillep]

Hmm I don't like this change. Yes, it fixes the issue, but it looks more like a dirty patch than a solution (fixing the symptom, not the cause).

What is the cause? Maybe the include be set in some other class?

[PalumboN]

Helloooo, I come with comments (but not solutions :P).

Mmm I see two problems (one in the solution and other in the issue):

1. I agree with Guille. Anyway, does this solution work? As both subclasses are overriding the method, the include won't be set in the header file. Am I right? Was it tested?

2. Soooo, the real problem is that declareCVarsIn: is called for each concrete class. There are two concrete subclasses for AbstractComposedImageAccess class, then this method will be executed twice (logging the waring inside addHeaderFile: method):

   declareCVarsIn: aCCodeGenerator
   
   aCCodeGenerator
       addHeaderFile:'<sys/stat.h> /* for e.g. mkdir */'

I don't see a good solution for this: moved to another hierarchy as Guille says seems to be the best, but in that case the header definition will be disconnected from the code that uses it...

It looks like Slang is not prepared for the subclassification that we try to do here (having 2 subclasses), at least for this kind of definitions.

[guillep]

We talked with @RenaudFondeur and we decided to add a couple of good comments to these methods, at least they will not remain just empty. It looks like a good compromise solution.