Added cached variable WORKBENCH_QT5_DEPRECATED_FATAL_ERROR to...

Added cached variable WORKBENCH_QT5_DEPRECATED_FATAL_ERROR to src/CMakeLists.txt.  When WORKBENCH_QT5_DEPRECATED_FATAL_ERROR is TRUE, a compiler definition (WORKBENCH_REPLACE_QT_DEPRECATED) is used with #ifdef/#else/#endif in the source code to allow usage of methods that replace the obsolete functions.  Examples include using std::sort() in place of qSort() and QDateTime::setOffsetFromUtc() in place of QDateTime::setUtcOffset().