qdoc didn't handle this. This update fixes most of what was wrong,
but tuning the details of the namespace reference pages might follw.
We have namespace Qt as an exaqmple. Most of the elements in the Qt
namespace are in QtCore, but a few functions are declared in QtGui.
Before this update, qdoc used the hack of using #ifdef to remove the
declarations from qtextdocument.h in QtGui and .cpp and then added
them back into qtnamespace.h and .cpp in QtCore.
Now that hack is no longer necessary. The functions in the Qt namespace
that are declared in QtGui are documented there, but the documentation
is linked to from the namespace reference page, which remains in QtCore.
That is, only one \namespace command is used to document the Qt namespace,
and it appears in qnamespace.qdoc where it always did, but the documentation
for the Qt namespace functions declared in QtGui is now appears in
qtextdocument.cpp where it belongs.
Change-Id: Ic5888875c3b8310a3dba244475e2a6c3bc0c1808
Task-number: QTBUG-67267
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
e3e0a6d6d6