File extension is unknown when using encode()

[Dimitar Misev]

This will result in a rasql_1.unknown file, but should be a rasql_1.png

rasql -q 'select encode(c, "PNG") from mr as c' --out file

Should be fixed in source:qlparser/qtencode.cc, an example on how to fix it can probably be found in source:qlparser/qtconversion.cc

[uadhikari]

The query works for me.