Implement compound operator patching.

Assets/Cryville/Common/Pdt/PdtEvaluatorBase.cs

@@ -34,6 +34,16 @@ namespace Cryville.Common.Pdt {
 			}
 		}
 		/// <summary>
+		/// Patches an expression with a lefthand variable and a compound operator.
+		/// </summary>
+		/// <param name="target">The name of the lefthand variable.</param>
+		/// <param name="op">The name of the compound operator.</param>
+		/// <param name="exp">The expression.</param>
+		public void PatchCompound(int target, int op, PdtExpression exp) {
+			exp.Instructions.AddFirst(new PdtInstruction.PushVariable(target));
+			exp.Instructions.AddLast(new PdtInstruction.Operate(op, 2));
+		}
+		/// <summary>
 		/// Optimizes an expression by merging its instructions.
 		/// </summary>
 		/// <param name="exp">The expression to optimize.</param>