Fix few minor mistakes

docs/simplesamlphp-authsource.md

docs/simplesamlphp-customauth.md

docs/simplesamlphp-errorhandling.md

docs/simplesamlphp-maintenance.md

docs/simplesamlphp-nostate.md

docs/simplesamlphp-sp-migration.md

docs/simplesamlphp-theming.md

lib/SimpleSAML/Auth/ProcessingChain.php

lib/SimpleSAML/Auth/Source.php

lib/SimpleSAML/Error/Exception.php

lib/SimpleSAML/Error/UnserializableException.php

lib/SimpleSAML/Memcache.php

lib/SimpleSAML/Metadata/MetaDataStorageHandlerPdo.php

lib/SimpleSAML/Stats.php

lib/SimpleSAML/Utilities.php

lib/SimpleSAML/XHTML/IdPDisco.php

modules/consent/lib/Auth/Process/Consent.php

modules/ldap/lib/ConfigHelper.php

modules/saml/www/disco.php

www/_include.php