Fix the changed APIs in C++ API rendering path.
- Some includes have moved to QtOpenGL module from QtGui
- Some APIs have been removed, and require conversion to available APIs or other sort of replacement
- QRegExp to be replaced with QRegularExpression
- QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_2_1>(); has been removed
- glPointSize is missing, as a result of the previous item