Add comphelper/configuration.hxx functions to unusedcode.exclude

The functionality in comphelper/configuration.hxx is used by C++ headers to
simplify configuration access that are generated via
officecfg/Package_cppheader.mk.

Change-Id: I85d26309ec8c4f8ac5cde773fd3298a699bad030

unusedcode.exclude

@@ -24,3 +24,6 @@ apitest::XPropertySet::testAddVetoableChangeListener()
 apitest::XPropertySet::testRemovePropertyChangeListener()
 apitest::XPropertySet::testRemoveVetoableChangeListener()
 apitest::XSpreadsheetDocument::testGetSheets()
+comphelper::detail::ConfigurationWrapper::getGroupReadWrite(boost::shared_ptr<comphelper::ConfigurationChanges> const&, rtl::OUString const&) const
+comphelper::detail::ConfigurationWrapper::getLocalizedPropertyValue(rtl::OUString const&) const
+comphelper::detail::ConfigurationWrapper::setLocalizedPropertyValue(boost::shared_ptr<comphelper::ConfigurationChanges> const&, rtl::OUString const&, com::sun::star::uno::Any const&) const