This adds three categories:
- qt.core.library
- qt.core.plugin.loader
- qt.core.plugin.factoryloader
plus the "qt.core.plugin.elfparser" category (only available in
developer builds).
All three use the new Q_LOGGING_CATEGORY_WITH_ENV_OVERRIDE technique
which enables their debugging if the QT_DEBUG_PLUGINS=1 variable is set.
As a consequence, some warnings were downgraded to debug messages. I've
only left as warnings situations where a real problem occurred, since
they now get printed by default: failures to open or mmap a file,
corrupt plugin metadata (but not scan of non-plugins), use of
QPluginLoader with a static build of Qt.
Drive-by update of some messages to make them prettier and/or use
qUtf16Printable().
Change-Id: I3eb1bd30e0124f89a052fffd16a752acfe89c19e
Reviewed-by: Kai Koehne <kai.koehne@qt.io>