[fix] sjp engine - convert enginename to a latin1 compliance name
The engine name is not only a *name* its also a identifier that is used in
logs, HTTP headers and more. Unicode characters in the name of an engine could
cause various issues.
Closes: https://github.com/searxng/searxng/issues/1544
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>