Add meta-definitions for AST types

- The big change here is that all the definitions for syntax-node classes have been macro-ized, to that we can do light metaprogramming over them
  - The use of macros for this has big down-sides, but I'm not quite ready to do anything more heavy-weight right now
  - The macro-ized definitions can be included multiple times, to generate different declarations/code as needed

- The first example of using this meta-programming facility is a new visitor system
  - The actual visitor base classes and the dispatch logic are all generated from the meta-files

- There was only one visitor left in the code: the semantics checker, so that was ported to the new system.

- All current test cases pass, so *of course* that means all is well.

1 files changed, 10 insertions, 0 deletions

diff --git a/source/slang/syntax-defs.h b/source/slang/syntax-defs.h
new file mode 100644
index 000000000..4ff4a55a6
--- /dev/null
+++ b/source/slang/syntax-defs.h
@@ -0,0 +1,10 @@
+// syntax-defs.h
+
+#include "syntax-base-defs.h"
+
+#include "expr-defs.h"
+#include "decl-defs.h"
+#include "modifier-defs.h"
+#include "stmt-defs.h"
+#include "type-defs.h"
+#include "val-defs.h"