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/Common/DataTypes.swift

@@ -424,19 +424,30 @@ public class P4BooleanValue: P4DataValue {
   }
 }
 
+public enum BitWidth: Equatable {
+  case Infinite
+  case Width(Int)
+}
+
 /// A P4 int type
 public struct P4Int: P4Type {
-  public init() {}
+  let width: BitWidth
+
+  public init(_ width: BitWidth = BitWidth.Infinite) {
+    self.width = width
+  }
 
   public var description: String {
-    return "Int"
+    return "Int (width: \(self.width))"
   }
+
   public func eq(rhs: P4Type) -> Bool {
     return switch rhs {
-    case is P4Int: true
+    case let rrhs as P4Int: rrhs.width == self.width
     default: false
     }
   }
+
   public func def() -> P4DataValue? {
     return P4IntValue(withValue: 0)
   }
@@ -444,12 +455,16 @@ public struct P4Int: P4Type {
 
 /// An instance of a P4 integer
 public class P4IntValue: P4DataValue {
+
+  let int_type: P4Int
+
   public func type() -> P4Type {
-    return P4Int()
+    return int_type
   }
 
   let value: Int
-  public init(withValue value: Int) {
+  public init(withValue value: Int, andWidth width: BitWidth = BitWidth.Infinite) {
+    self.int_type = P4Int(width)
     self.value = value
   }