pyqt broke sip4 compatibility in 5.15.6, and there is no more maintainer
of the KF Python bindings to fix things.

Future support might need different code, so no advantage in keeping the
old code around.

Macros Q_NAMESPACE_EXPORT should be used without semicolon
https://doc.qt.io/qt-5/qobject.html#Q_NAMESPACE_EXPORT

This generates warning: extra ‘;’ [-Wpedantic]

This fixes the build with Qt6 on Android.

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So that #include <kconfig_version.h> still works after changing its
location in the previous commit.

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The eliminated duplication of the composite condition was error-prone
and less readable.

entryMap is ordered by the group name first. So there is no need to
iterate over the entire map to process entries whose group names start
with some prefix. Find the group name prefix's lower bound and iterate
over the proper subrange instead. This should be much faster, especially
if the subrange's size is much less than the entryMap's size.

Adjust isGroupOrSubGroupMatch() helper function to assert the extracted
startsWith() condition instead of rechecking it. Pass
KEntryMapConstIterator in place of the group name to this function in
order to simplify its callers' code. Reuse this helper function in
KConfigPrivate::copyGroup().