[Qbs] qbs, qmake and filename case sensitivity

[Timur Kristóf]

Hi Chris,

> I am not sure what is the best behaviour:
> - QMake being convenient.
> - Qbs being strict.
> 
> Should Qbs mimic what qmake does?

I would suggest something in between: be convenient like qmake, but
generate a warning when the filename doesn't exactly match.

Alternatively, maybe add a property to the Project element which
controls the behaviour, so either it's case sensitive, or insensitive,
or insensitive but with warnings.

Cheers,
Tim