grammar,compiler: Add Support For Fixed-Width Integers

Distinguishing between signed and unsigned fixed-width integer
types must still be done.

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

Sources/P4Runtime/CodeGen.swift

@@ -17,6 +17,7 @@
 
 import Common
 import P4Lang
+import P4Protos
 
 public struct Generated {
   let gen: String
@@ -48,13 +49,12 @@ public struct CodeGenerator: LanguageVisitor {
     return visitor.start(node, context: generated)
   }
 
-  /// TODO: Can we generate these implementations somehow?
-
   public typealias Context = Generated
 
   public func visit(
     _ v: Program, _ c: VisitorContext<Generated>
   ) -> Result<VisitorContext<Generated>> {
+
     var result: Result<VisitorContext<Generated>> = Fold(
       input: v.types, initial: .Ok(c.next(uc: c.getUserContext().append("[")))
     ) { (current, acc) in