make ProString c'tors explicit only when not building qmake
make ProString c'tors explicit only when not building qmake

otherwise it's impossible to migrate the qmake generators to this.

Change-Id: I70c848da2ce428706b960c3c1434c26f7e3a9447
Reviewed-by: Daniel Teske <d8a411aec9a206efedb4d45b75fe8d13f1e2b628@nokia.com>

xianian/qt-creator,malikcjm/qtcreator,martyone/sailfish-qtcreator,richardmg/qtcreator,farseerri/git_code,omniacreator/qtcreator,farseerri/git_code,richardmg/qtcreator,amyvmiwei/qt-creator,amyvmiwei/qt-creator,Distrotech/qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,maui-packages/qt-creator,xianian/qt-creator,farseerri/git_code,maui-packages/qt-creator,colede/qtcreator,maui-packages/qt-creator,syntheticpp/qt-creator,danimo/qt-creator,farseerri/git_code,malikcjm/qtcreator,farseerri/git_code,kuba1/qtcreator,syntheticpp/qt-creator,duythanhphan/qt-creator,syntheticpp/qt-creator,darksylinc/qt-creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,malikcjm/qtcreator,amyvmiwei/qt-creator,malikcjm/qtcreator,duythanhphan/qt-creator,colede/qtcreator,AltarBeastiful/qt-creator,Distrotech/qtcreator,martyone/sailfish-qtcreator,richardmg/qtcreator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,xianian/qt-creator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,omniacreator/qtcreator,danimo/qt-creator,duythanhphan/qt-creator,colede/qtcreator,xianian/qt-creator,danimo/qt-creator,maui-packages/qt-creator,maui-packages/qt-creator,omniacreator/qtcreator,darksylinc/qt-creator,kuba1/qtcreator,omniacreator/qtcreator,duythanhphan/qt-creator,danimo/qt-creator,amyvmiwei/qt-creator,farseerri/git_code,colede/qtcreator,richardmg/qtcreator,xianian/qt-creator,colede/qtcreator,Distrotech/qtcreator,xianian/qt-creator,Distrotech/qtcreator,amyvmiwei/qt-creator,richardmg/qtcreator,malikcjm/qtcreator,kuba1/qtcreator,maui-packages/qt-creator,syntheticpp/qt-creator,farseerri/git_code,xianian/qt-creator,AltarBeastiful/qt-creator,kuba1/qtcreator,martyone/sailfish-qtcreator,duythanhphan/qt-creator,colede/qtcreator,darksylinc/qt-creator,kuba1/qtcreator,amyvmiwei/qt-creator,darksylinc/qt-creator,Distrotech/qtcreator,omniacreator/qtcreator,omniacreator/qtcreator,AltarBeastiful/qt-creator,maui-packages/qt-creator,xianian/qt-creator,Distrotech/qtcreator,malikcjm/qtcreator,duythanhphan/qt-creator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,danimo/qt-creator,darksylinc/qt-creator,danimo/qt-creator,duythanhphan/qt-creator,richardmg/qtcreator,martyone/sailfish-qtcreator,syntheticpp/qt-creator,martyone/sailfish-qtcreator,danimo/qt-creator,malikcjm/qtcreator,kuba1/qtcreator,martyone/sailfish-qtcreator,colede/qtcreator,AltarBeastiful/qt-creator,omniacreator/qtcreator,xianian/qt-creator,kuba1/qtcreator,kuba1/qtcreator,syntheticpp/qt-creator,darksylinc/qt-creator,kuba1/qtcreator,darksylinc/qt-creator,farseerri/git_code,Distrotech/qtcreator,darksylinc/qt-creator,AltarBeastiful/qt-creator,richardmg/qtcreator