patchreview: Restore libkomparediff2 5.0 support

Failed with:
/usr/include/libkomparediff2/kompare.h:93:32: error: 'QString::QString(const char*)' is private within this context
    QString _localDestination = "",
                                ^~

plugins/patchreview/CMakeLists.txt

@@ -21,6 +21,7 @@ kde_enable_exceptions()
 
 if(LibKompareDiff2_VERSION VERSION_LESS 5.1)
     remove_definitions(
+        -DQT_NO_CAST_FROM_ASCII
         -DQT_NO_SIGNALS_SLOTS_KEYWORDS
     )
 endif()