move qdoc back to qttools

we can do that now, as the bootstrap lib is now a properly exported
module, and qmldevtools is now bootstrapped as well.

this removes the abomination of a copy of the qml parser in qtbase.
unfortunately qtbase/2422251ee5025a067b14b989153764ab36e43f10 is
reverted, as qtdeclarative is still missing the respective change.

this introduces no regression in discoverability or usability, as a full
doc build already needed qttools - for qhelpgenerator.

Change-Id: Ic9c4c9732ddf5998637b9e42e27939ba50b31479
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>