Add support for a  QTDOCTAG environment variable, so that Qt dox don't need to be generated but can use a pre-generated tag file. Removes the need for Qt sources on the apidox-generating machine.
Add support for a  QTDOCTAG environment variable, so that Qt dox don't need to be generated but can use a pre-generated tag file. Removes the need for Qt sources on the apidox-generating machine.

svn path=/trunk/KDE/kdepim/; revision=424120

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi