debugger: prevent double insertion of breakpoint markers
debugger: prevent double insertion of breakpoint markers

Change-Id: Ie5a8625ed2887831600f1835777f9f681b012f15
Reviewed-on: http://codereview.qt.nokia.com/794
Reviewed-by: hjk <6fac1c92f5b9c7890a04d7f8a9d8912d16355eac@ovi.com>

dmik/qt-creator-os2,kuba1/qtcreator,farseerri/git_code,danimo/qt-creator,KDAB/KDAB-Creator,KDE/android-qt-creator,amyvmiwei/qt-creator,azat/qtcreator,bakaiadam/collaborative_qt_creator,duythanhphan/qt-creator,richardmg/qtcreator,KDE/android-qt-creator,farseerri/git_code,Distrotech/qtcreator,xianian/qt-creator,duythanhphan/qt-creator,ostash/qt-creator-i18n-uk,xianian/qt-creator,Distrotech/qtcreator,malikcjm/qtcreator,richardmg/qtcreator,dmik/qt-creator-os2,colede/qtcreator,martyone/sailfish-qtcreator,colede/qtcreator,omniacreator/qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,syntheticpp/qt-creator,hdweiss/qt-creator-visualizer,syntheticpp/qt-creator,amyvmiwei/qt-creator,maui-packages/qt-creator,ostash/qt-creator-i18n-uk,richardmg/qtcreator,KDAB/KDAB-Creator,darksylinc/qt-creator,colede/qtcreator,azat/qtcreator,duythanhphan/qt-creator,farseerri/git_code,omniacreator/qtcreator,darksylinc/qt-creator,Distrotech/qtcreator,jonnor/qt-creator,darksylinc/qt-creator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,maui-packages/qt-creator,KDE/android-qt-creator,bakaiadam/collaborative_qt_creator,AltarBeastiful/qt-creator,kuba1/qtcreator,martyone/sailfish-qtcreator,colede/qtcreator,KDE/android-qt-creator,Distrotech/qtcreator,duythanhphan/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,richardmg/qtcreator,ostash/qt-creator-i18n-uk,bakaiadam/collaborative_qt_creator,farseerri/git_code,azat/qtcreator,Distrotech/qtcreator,AltarBeastiful/qt-creator,KDAB/KDAB-Creator,amyvmiwei/qt-creator,colede/qtcreator,jonnor/qt-creator,kuba1/qtcreator,azat/qtcreator,amyvmiwei/qt-creator,azat/qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,jonnor/qt-creator,richardmg/qtcreator,xianian/qt-creator,xianian/qt-creator,maui-packages/qt-creator,hdweiss/qt-creator-visualizer,martyone/sailfish-qtcreator,danimo/qt-creator,duythanhphan/qt-creator,kuba1/qtcreator,darksylinc/qt-creator,kuba1/qtcreator,omniacreator/qtcreator,danimo/qt-creator,bakaiadam/collaborative_qt_creator,AltarBeastiful/qt-creator,amyvmiwei/qt-creator,dmik/qt-creator-os2,omniacreator/qtcreator,malikcjm/qtcreator,jonnor/qt-creator,KDE/android-qt-creator,omniacreator/qtcreator,jonnor/qt-creator,danimo/qt-creator,danimo/qt-creator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,KDAB/KDAB-Creator,dmik/qt-creator-os2,syntheticpp/qt-creator,ostash/qt-creator-i18n-uk,dmik/qt-creator-os2,kuba1/qtcreator,KDAB/KDAB-Creator,martyone/sailfish-qtcreator,xianian/qt-creator,darksylinc/qt-creator,Distrotech/qtcreator,danimo/qt-creator,KDAB/KDAB-Creator,AltarBeastiful/qt-creator,maui-packages/qt-creator,martyone/sailfish-qtcreator,ostash/qt-creator-i18n-uk,duythanhphan/qt-creator,colede/qtcreator,farseerri/git_code,amyvmiwei/qt-creator,farseerri/git_code,maui-packages/qt-creator,xianian/qt-creator,kuba1/qtcreator,bakaiadam/collaborative_qt_creator,hdweiss/qt-creator-visualizer,ostash/qt-creator-i18n-uk,darksylinc/qt-creator,malikcjm/qtcreator,syntheticpp/qt-creator,ostash/qt-creator-i18n-uk,Distrotech/qtcreator,syntheticpp/qt-creator,omniacreator/qtcreator,colede/qtcreator,hdweiss/qt-creator-visualizer,KDE/android-qt-creator,azat/qtcreator,kuba1/qtcreator,hdweiss/qt-creator-visualizer,bakaiadam/collaborative_qt_creator,xianian/qt-creator,richardmg/qtcreator,richardmg/qtcreator,malikcjm/qtcreator,darksylinc/qt-creator,amyvmiwei/qt-creator,bakaiadam/collaborative_qt_creator,darksylinc/qt-creator,hdweiss/qt-creator-visualizer,AltarBeastiful/qt-creator,malikcjm/qtcreator,danimo/qt-creator,xianian/qt-creator,dmik/qt-creator-os2,dmik/qt-creator-os2,omniacreator/qtcreator,martyone/sailfish-qtcreator,farseerri/git_code,duythanhphan/qt-creator,malikcjm/qtcreator,kuba1/qtcreator,syntheticpp/qt-creator,KDE/android-qt-creator,jonnor/qt-creator,maui-packages/qt-creator,maui-packages/qt-creator,malikcjm/qtcreator,KDE/android-qt-creator,farseerri/git_code,syntheticpp/qt-creator