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/Call.swift

@@ -42,7 +42,7 @@ public struct Parameter: CustomStringConvertible, Equatable {
     if let param_direction = self.type.direction(),
       param_direction == Direction.In || param_direction == Direction.InOut
     {
-      if !(argument.argument is EvaluatableLValueExpression) {
+      if !(argument.argument is P4LValueExpression) {
         return false
       }
     }
@@ -125,9 +125,9 @@ public struct ArgumentList {
 
 public struct Argument {
   public let index: Int
-  public let argument: EvaluatableExpression
+  public let argument: P4Expression
 
-  public init(_ argument: EvaluatableExpression, atIndex index: Int) {
+  public init(_ argument: P4Expression, atIndex index: Int) {
     self.argument = argument
     self.index = index
   }