I suspect it was a79f70, that's when setCustomProperty() and friends changed.

(slightly reformatted so it doesn't completely break preformatted display)

g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -DQT_WEBKIT -DQCAD_DLL -DPTHREADS
    -DHAVE_PTHREAD_H -DQT_NO_DEBUG -DQT_WEBKIT_LIB -DQT_SCRIPT_LIB
    -DQT_SCRIPTTOOLS_LIB -DQT_SVG_LIB -DQT_SQL_LIB -DQT_XMLPATTERNS_LIB -DQT_XML_LIB
    -DQT_OPENGL_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -DQT_SHARED
    -I/usr/share/qt4/mkspecs/linux-g++-64 -I. -I/usr/include/qt4/QtHelp
    -I/usr/include/qt4/QtDesigner -I/usr/include/qt4/QtUiTools
    -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtNetwork -I/usr/include/qt4/QtGui
    -I/usr/include/qt4/QtOpenGL -I/usr/include/qt4/QtXml
    -I/usr/include/qt4/QtXmlPatterns -I/usr/include/qt4/QtSql
    -I/usr/include/qt4/QtSvg -I/usr/include/qt4/QtScriptTools
    -I/usr/include/qt4/QtScript -I/usr/include/qt4/QtWebKit -I/usr/include/qt4
    -I../../../src/core -I../../../src/core/math -I../../../src/grid
    -I../../../src/snap -I../../../src/gui -I../../../src/entity
    -I../../../src/operations -I../../../src/scripting -I../../../src/stemmer
    -I../../../src/scripting/ecmaapi -I../../../src/scripting/ecmaapi/generated
    -I../../../src/scripting/ecmaapi/adapters -I../../../src/io/dxf
    -I../../../src/spatialindex -I../../../src/3rdparty -I/usr/X11R6/include
    -Irelease -o release/MainWindow.o MainWindow.cpp
In file included from MainWindow.cpp:13:0:
../../../src/spatialindex/RSpatialIndexNavel.h: In member function ‘virtual void
    RSpatialIndexNavel::Visitor::visitData(std::vector<const SpatialIndex::IData*>&)’:
../../../src/spatialindex/RSpatialIndexNavel.h:191:77: warning: format ‘%Ld’
    expects argument of type ‘long long int’, but argument 2 has type
    ‘SpatialIndex::id_type {aka long int}’ [-Wformat]
MainWindow.cpp: In constructor ‘MainWindow::MainWindow(QWidget*)’:
MainWindow.cpp:79:54: error: no matching function for call to
    ‘RLineEntity::setCustomProperty(const char [14], int)’
MainWindow.cpp:79:54: note: candidate is:
../../../src/core/RObject.h:165:10: note:
    void RObject::setCustomProperty(const QString&, const QString&, const QVariant&)
../../../src/core/RObject.h:165:10: note:   candidate expects 3 arguments, 2 provided
MainWindow.cpp:80:66: error: no matching function for call to
    ‘RLineEntity::setCustomProperty(const char [17], const char [10])’
MainWindow.cpp:80:66: note: candidate is:
../../../src/core/RObject.h:165:10: note:
    void RObject::setCustomProperty(const QString&, const QString&, const QVariant&)
../../../src/core/RObject.h:165:10: note:   candidate expects 3 arguments, 2 provided
make[4]: *** [release/MainWindow.o] Error 1

Linux, Qt 4.8.1, GCC 4.6.4