Throw an error when deserializing a bad type

This error should never be encountered, as long as we always update the get
function when the put function is, as required by get . put == id.
Remove catch-all match in Declaration

These ought to actually be written out, as the previous TODO message stated,
but at least this way the compiler will warn us when adding a new Decl.
Add invalid serialization errors to Module.hs
Fix typo
Merge pull request #321 from Sheeo/sourcesyntax-matches

Incomplete matches in sourcesyntax