Apply filetype-specific indentation settings for newly opened files

Fix the check enabling filetype-specific indentation settings to also
pass if the document has no filetype set yet, e.g. when opening it.
Update Scintilla to version 3.4.1
Fix const promotion with updated Scintilla
Update mappings for new Scintilla
Fix a typo in the update script
Merge branch 'scintilla-update-341'