Quoting variable filter arguments

You can now quote the argument to a variable filter in a style file.

A simple contrived example:

# Fix short form and mis-spelling
highway=residential { set name '${name|subst:"(Raod|Rd)~>Road"}' ; }

For backward compatibility you do not have to do this and all existing styles should work as they are. However I would recommend that you start to quote all arguments that are more complex than a simple word. Before this change it was impossible to use a pipe symbol within a regular expression since it would be seen as the start of the next filter.