Return instruction pops zero or one item instead of all.

Exception of catch block does not have to be consumed.
Related to #185

ICSharpCode.Decompiler/CecilExtensions.cs

@@ -59,7 +59,7 @@ namespace ICSharpCode.Decompiler
 			throw new NotSupportedException ();
 		}
 		
-		public static int? GetPopDelta(this Instruction instruction)
+		public static int? GetPopDelta(this Instruction instruction, MethodDefinition methodDef)
 		{
 			OpCode code = instruction.OpCode;
 			switch (code.StackBehaviourPop) {
@@ -93,7 +93,7 @@ namespace ICSharpCode.Decompiler
 
 				case StackBehaviour.Varpop:
 					if (code == OpCodes.Ret)
-						return null;
+						return methodDef.ReturnType.IsVoid() ? 0 : 1;
 
 					if (code.FlowControl != FlowControl.Call)
 						break;

ICSharpCode.Decompiler/FlowAnalysis/SsaFormBuilder.cs

@@ -129,7 +129,7 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 					continue;
 				}
 				
-				int popCount = inst.GetPopDelta() ?? stackSize;
+				int popCount = inst.GetPopDelta(method) ?? stackSize;
 				stackSize -= popCount;
 				if (stackSize < 0)
 					throw new InvalidProgramException("IL stack underflow");

ICSharpCode.Decompiler/ILAst/ILAstBuilder.cs

@@ -260,7 +260,7 @@ namespace ICSharpCode.Decompiler.ILAst
 					EndOffset   = inst.Next != null ? inst.Next.Offset : methodDef.Body.CodeSize,
 					Code        = code,
 					Operand     = operand,
-					PopCount    = inst.GetPopDelta(),
+					PopCount    = inst.GetPopDelta(methodDef),
 					PushCount   = inst.GetPushDelta()
 				};
 				if (prefixes != null) {
@@ -701,8 +701,9 @@ namespace ICSharpCode.Decompiler.ILAst
 						};
 						// Handle the automatically pushed exception on the stack
 						ByteCode ldexception = ldexceptions[eh];
-						if (ldexception.StoreTo.Count == 0) {
-							throw new Exception("Exception should be consumed by something");
+						if (ldexception.StoreTo == null || ldexception.StoreTo.Count == 0) {
+							// Exception is not used
+							catchBlock.ExceptionVariable = null;
 						} else if (ldexception.StoreTo.Count == 1) {
 							ILExpression first = catchBlock.Body[0] as ILExpression;
 							if (first != null &&