DbMetal: Don't know how to convert the SQL type 'xml' into a managed type

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What steps will reproduce the problem?
1. Create Postgresql table with a column of type xml
2. Run DbMetal.exe
3. Get greeted by it not knowing how to use it.

Please provide any additional information below.

I tried adding an entry for xml in SchemaLoader.TypeMapping.cs, to map it as a 
string. I still get the same error. What other steps do I need to know in order 
to get my type mapped?

Original issue reported on code.google.com by faboster on 19 Mar 2014 at 1:13