Autogen: Improve error detection during configuration
cmQtAutoGenInitializer::InitCustomTargets and cmQtAutoGenInitializer::SetupCustomTargets now return their success value which gets evaluated and passed on by the caller (cmGlobalGenerator). Checks for the existance of the moc/uic/rcc binaries have been introduces in cmQtAutoGenInitializer. Additionally they get called once with a "-h" argument to determine if they're functional. This way any binary-not-found problem is caught during the configuration phase.