Support pattern matching in quasiquotes

[LPTK]

Currently, pattern matching and partial function syntaxes (and derived) are not supported. Implement a virtualization scheme to support them.

[LPTK]

Note that there are now the required definitions in place for virtualized pattern matching, in squid/lib/matching.scala. We just need to adapt ModularEmbedding to convert pattern matching syntax to these. And ideally, of course, make the default IRs smart about handling pattern-matching.