This is a very simple sema implementation, and just required AST node
plus the existing diagnostics. This patch adds tests and adds the AST
node required, plus enables it for 'init' and 'shutdown' (only!)
These two constructs are very simple and similar, and only support 3
different clauses, two of which are already implemented. This patch
adds AST nodes for both constructs, and leaves the device_num clause
unimplemented, but enables the other two.