[Development] QMake behaviour change

[Daniel Teske]

> - Means that source code where headers and sources are split into
> different directories all of a sudden depends on relative paths to all
> files
See VPATH, which Ossi already mentioned in the bug report.

> - Behaves differently from QtCreator (tested with a rather old version
> 2.5.2).
What exactly did you test? That Creator can find the headers? That's not 
testing anything of relevenace to the qmake behaviour.

daniel