Fix generation of the forward header for QFunctionPointer

The forward header for QFunctionPointer was being generated by accident,
apparently syncqt is confused because of some of the preceding lines. If
the lines are rearranged or removed, the header won't be generated. Not
sure if there's much value in generating a header for it, but at least
one of Qt sources (qeglfsemulatorintegration.h) is using it in an
include statment, and there's a chance it's used in the user code as
well.

Change-Id: Iced505881ddb07e7a8336fcdfb7d3e5397c6466c
Pick-to: 6.4 6.3 6.2 5.15
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qglobal.cpp

@@ -1058,7 +1058,7 @@ static_assert(sizeof(qint64) == 8, "Internal error, qint64 is misdefined");
 */
 
 /*! \typedef QFunctionPointer
-    \relates <QtGlobal>
+    \relates <QFunctionPointer>
 
     This is a typedef for \c{void (*)()}, a pointer to a function that takes
     no arguments and returns void.

src/corelib/global/qglobal.h

@@ -654,6 +654,9 @@ Q_CORE_EXPORT void qBadAlloc();
 template <typename T>
 inline T *q_check_ptr(T *p) { Q_CHECK_PTR(p); return p; }
 
+#if 0
+#pragma qt_class(QFunctionPointer)
+#endif
 typedef void (*QFunctionPointer)();
 
 #if !defined(Q_UNIMPLEMENTED)