compiler, runtime: Begin Runtime Refactor

Ultimately, the goal is to completely separate the compilation from
the runtime to make it possible to have the interpreter/evaluator
be "just another" entity that can perform meaningful work when
given a parsed GP4 program.

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/Common/Support.swift

@@ -106,3 +106,6 @@ public func Fold<T, A>(input: [T], initial: A, block: (T, A) -> A) -> A {
 
 @freestanding(codeItem) public macro MustOr<E, N>(result: E, thing: E?, or: N) =
   #externalMacro(module: "Macros", type: "MustOr")
+
+@attached(peer) public macro DeriveCompilableStatement() =
+  #externalMacro(module: "Macros", type: "DeriveCompilableStatement")