qmake doc moved to qtbase

Change-Id: Ic6a38c9e5acf3d5c35032bf7e6cbc805079e5399
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>