C++: Fix memory leak in preprocessor.
C++: Fix memory leak in preprocessor.

This addresses the main memory leak revealed in QTCREATORBUG-7645.
The other leaks seem to have their origin in Qt.

Task-Number: QTCREATORBUG-7645.
Change-Id: I77f45449416c143b222ed5f5c905cba9674f95bb
Reviewed-by: Christian Kamm <afb711f88e55c3f2d1b57cdc8d937fab8e46ae57@incasoftware.de>

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