Replaces hard-coded name by a variable

It will be useful when porting to Qt5.

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Adds portable headers

Adds the portable headers way, that works with Qt4 and Qt5 without change:

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>
Adds initial Qt5 support

Signed-off-by: Luís Pereira <luis.artur.pereira@gmail.com>